Aoki, M. (1967) Optimization of stochastic systems. Academic Press.Google Scholar

Arnold, S. J. (1983) Morphology, performance and fitness. American Zoologist 38:709–19; 23:347–61.Google Scholar

Arnold, S. J. & Wade, M. J. (1984) On the measurement of natural and sexual selection: Applications. Evolution 38:720–34.CrossRefGoogle ScholarPubMed

Barnard, C. J. & Brown, C. A. J. (1981) Prey size selection and competition in the common shrew (Sorex araneus). Behavioural Ecology and Sociobiobgy 8:239–43.CrossRefGoogle Scholar

Barnard, C. J. & Brown, C. A. J. (1985) Competition affects risk-sensitivity in foraging shrews. Behavioural Ecology and Sociobiology 16:379–82.CrossRefGoogle Scholar

Barnard, C. J. & Brown, C. A. J. (1985a) Risk sensitivity in foraging common shrews (Sorex araneus L.). Behavioural Ecology and Sociobiology 16:161–64.CrossRefGoogle Scholar

Barnard, C. J., Brown, C. A. J. & Gray-Wallis, F. J. (1983) Time and energy budgeting and competition in common shrews (Sorex araneus). Behavioural Ecology and Sociobiology 13:13–18.CrossRefGoogle Scholar

Barnard, C. J., Brown, C. A. J., Houston, A. I. & McNamara, J. M. (1985) Risk-sensitive foraging in common shrews: An interruption model and the effects of mean and variance in reward rate. Behavioural Ecology and Sociobiology 18:139–46.CrossRefGoogle Scholar

Barnard, C. J. & Hurst, J. (1987) Time constraints and prey selection in common shrews (Sorex araneus). Animal Behaviour 35.CrossRefGoogle Scholar

Barnard, C. J. & Thompson, D. B. A. (1985) Gulls and plovers: The ecology and behaviour of mixed-species feeding groups. Croom Helm.Google Scholar

Baum, W. M. (1974) Choice in free-ranging wild pigeons. Science 185:78–79.CrossRefGoogle ScholarPubMed

Baum, W. M. (1974a) On two types of deviation from the matching law: Bias and undermatching. Journal of the Experimental Analysis of Behavior 22:231–42.CrossRefGoogle ScholarPubMed

Baum, W. M. (1983) Studying foraging in the psychological laboratory. In: Animal cognition and behavior, ed. Mellgren, R. L.. North-Holland.Google Scholar

Bellman, R. (1957) Dynamic programming. Princeton University Press.Google ScholarPubMed

Bellman, R. (1961) Adaptive control processes: A guided tour. Princeton University Press.Google Scholar

Bellman, R. & Dreyfus, S. E. (1962) Applied dynamic programming. Princeton University Press.CrossRefGoogle ScholarPubMed

Belovsky, G. E. (1981) Optimal activity times and habitat choice of moose. Oecologia 48:22–30.CrossRefGoogle ScholarPubMed

Bertsekas, D. P. (1976) Dynamic programming and stochastic control. Academic Press.Google Scholar

Bookstaber, R. & Langsam, J. (1985) On the optimality of coarse behaviour rules. Journal of Theoretical Biology 116:161–93.CrossRefGoogle Scholar

Brown, J. S. & Vincent, T. L. (1987) A theory for the evolutionary game. Theoretical Population Biology 31:140–66.Google Scholar

Bryant, D. M. & Westerterp, K. R. (1983) Time and energy limits to brood size in house martins (Delichon urbica). Journal of Animal Ecology 52:905–25.CrossRefGoogle Scholar

Busino, G. (1975) Sodologia e Storia. Guida.Google Scholar

Calder, W. A. III (in preparation) Territorially, body mass regulation, noeturnal energy conservation, and survivorship of the male broad-tailed hummingbird (Selasphorus platycercus).Google Scholar

Caraco, T. (1980) On foraging time allocation in a stochastic environment. Ecology 61:119–28.CrossRefGoogle Scholar

Caraco, T. (1981a) Energy budgets, risk and foraging preferences in dark-eyed juncos (Junco hyemalis). Behavioural Ecology and Sociobiology 8:213–17.CrossRefGoogle Scholar

Caraco, T. (1981b) Risk-sensitivity and foraging groups. Ecology 62:527–31.Google Scholar

Caraco, T. (1983) White-crowned sparrows (Zonotrichia leucophrys): Foraging preferences in a risky environment. Behavioural Ecology and Sociobiology 12:63–69.CrossRefGoogle Scholar

Caraco, T. & Chasin, M. (1984) Foraging preferences: Response to reward skew. Animal Behaviour 32:76–85.CrossRefGoogle Scholar

Caraco, T. & Lima, S. L. (1987) Survivorship, energy budgets and foraging risk. In: Quantitative analysis of behavior. Vol. 6: Foraging, ed. Commons, M. L., Kacelnik, A. & Shettleworth, S. J.. Erlbaum.Google Scholar

Caraco, T., Martindale, S. & Whittam, T. S. (1980) An empirical demonstration of risk sensitive foraging preferences. Animal Behaviour 28:820–30.CrossRefGoogle Scholar

Carpenter, F. L., Paton, D. C. & Hixon, M. A. (1983) Weight gain and adjustment of feeding territory size in migrant hummingbirds. Proceedings of the National Academy of Sciences (U.S.A.) 80:7259–63.CrossRefGoogle ScholarPubMed

Cartan, E. (1945) Les systemes differentiels exterieurs est leur applications geometrique. Exposes de Ceometrie, vol. 14. Hermann.Google Scholar

Case, D. A., Fantino, E. & Wixted, J. (1985) Human observing: Maintained by negative informative stimuli only if correlated with improvement in response efficiency. Journal of the Experimental Analysis of Behavior 43:289–300.CrossRefGoogle ScholarPubMed

Charnov, E. L. (1976) Optimal foraging: Attack strategy of a mantid. American Naturalist 110:141–51.CrossRefGoogle Scholar

Clark, C. W. (1987) The lazy, adaptable lions: A Markovian model of group foraging. Animal Behaviour 35:361–68.Google Scholar

Clark, C. W. & Levy, D. A. (in press) Diel vertical migrations of juvenile sockeye salmon and the antipredation window. American Naturalist.Google Scholar

Clark, C. W. & Mangel, M. (1986) The evolutionary advantages of group foraging. Theoretical Population Biology 30:45–75.Google Scholar

Collier, G. H. (1982) Determinants of choice. In: Nebraska Symposium on Motivation, ed. Bernstein, D.. University of Nebraska Press.Google Scholar

Collier, G. H. (1983) Life in a closed economy: The ecology of learning and motivation. Advances in analysis of behaviour. Vol. 3: Biological factors in learning, ed. Zeiler, M. D. & Harzem, P.. Wiley.Google Scholar

Collier, G. H., Johnson, D. F., Hill, W. L. & Kaufman, L. W. (1986) The economics of the law of effect. Journal of the Experimental Analysis of Behavior 46:113–36.CrossRefGoogle ScholarPubMed

Craig, R. B., De Angelis, D. L. & Dixon, K. R. (1979) Long- and short-term dynamic optimization models with application to the feeding strategy of the loggerhead shrike. American Naturalist 113:31–51.CrossRefGoogle Scholar

Crowcroft, P. (1955) The life of the shrew. Reinhardt.Google Scholar

Daan, S. (1981) Adaptive daily strategies in behavior. In: Handbook of behavioral neurobiology, vol. 4, ed. Aschoff, J.. Plenum.Google Scholar

Davies, N. B. (1977) Prey selection and the search strategy of the spotted flycatcher (Muscicapa striata): A field study on optimal foraging. Animal Behaviour 25:1016–33.CrossRefGoogle Scholar

Davies, N. B. & Houston, A. I. (1983) Time allocation between territories and flocks and owner-satellite conflict in foraging pred wagtails, Motacilla alba. Journal of Animal Ecology 52:621–34.CrossRefGoogle Scholar

Davison, M. C. (1972) Preference for mixed-interval versus fixed-interval schedules: Number of component intervals. Journal of the Experimental Analysis of Behavior 17:169–76.CrossRefGoogle ScholarPubMed

Dawkins, M. S. (1983) Battery hens name their price: Consumer demand theory and the measurement of ethological “needs.” Animal Behaviour 31:1195–1205.CrossRefGoogle Scholar

Dawkins, M. S. (in preparation) Behavioural deprivation: A central problem in animal welfare.Google Scholar

Dawkins, R. (1982) The extended phenotype. W. H. Freeman.Google Scholar

DeBenedictis, P. A., Gill, F. B., Hainsworth, F. R., Pyke, G. H. & Wolf, L. L. (1978) Optimal meal size in hummingbirds. American Naturalist 112:301–16.CrossRefGoogle Scholar

De Carlo, L. T. (1985) Matching and maximizing with variable-time schedules. Journal of the Experimental Analysis of Behavior 43:75–81.CrossRefGoogle ScholarPubMed

De Groot, M. H. (1970) Optimal statistical decisions. McGraw-Hill.Google Scholar

Dennett, D. C. (1971) Intentional systems. Journal of Philosophy 68:87–106.CrossRefGoogle Scholar

Dennett, D. C. (1983) Intentional systems in cognitive ethology: The “Planglossian paradigm” defended. Behavioral and Brain Sciences 6:343–90.CrossRefGoogle Scholar

Diamond, J. M., Karasov, W. H., Phan, D. & Carpenter, F. L. (1986) Digestive physiology is a determinant of foraging bout frequency in hummingbirds. Nature 320:62–63.CrossRefGoogle ScholarPubMed

Dill, L. M. (1983) Adaptive flexibility in the foraging behavior of fishes. Canadian Journal of Fisheries and Aquatic Science 40:398–408.CrossRefGoogle Scholar

Dinsmoor, J. A. (1983) Observing and conditioned reinforcement. Behavioral and Brain Sciences 6:693–728.CrossRefGoogle Scholar

Ekman, J. & Rosander, B. (1987) Starvation risk and flock size of the social forager: When is there a flocking cost? Theoretical Population Biology 31:167–77.Google Scholar

Engen, S., Saether, B.-E. & Stenseth, N. C. (in press) The effect of competition on the ranking of food items. American Naturalist.Google Scholar

Engen, S. & Stenseth, N. C. (in press) Optimal foraging theory: A settheoretical approach. Ecological Modelling.Google Scholar

Engen, S. & Stenseth, N. C. (submitted) Age-specific optimal diets and optimal foraging tactics: A life-historic approach.Google Scholar

Erwin, M. R. (1985) Foraging decisions, patch use, and seasonality in egrets (Aves: Ciconiiformes). Ecology 66:837–44.CrossRefGoogle Scholar

Fantino, E. & Abarca, N. (1985) Choice, optimal foraging, and the delay-reduction hypothesis. Behavioral and Brain Sciences 8:315–30.CrossRefGoogle Scholar

Fantino, E. & Case, D. A. (1983) Human observing: Maintained by stimuli correlated with reinforcement but not extinction. Journal of the Experimental Analysis of Behavior 40:193–210.CrossRefGoogle Scholar

Fantino, E., Case, D. A. & Altus, D. (1983) Observing reward-informative and -uninformative stimuli by normal children of different ages. Journal of Experimental Child Psychology 36:437–52.CrossRefGoogle Scholar

Fisher, R. A. (1930) The genetic theory of natural selection. Clarendon Press.Google Scholar

Freed, L. A. (1981) Loss of mass in breeding wrens: Stress or adaptation? Ecology 62:1179–86.CrossRefGoogle Scholar

Freeman, S. & MacFarland, D. J. (1982) The Darwinian objective function and adaptive behaviour. In: Functional ontogeny, ed. Morse, D. H. (1985) Reproductive success and foraging of the crab spider Misumena vatia. Oecologia 65:194–200.Google Scholar

Gillespie, R. G. & Caraco, T. (1987) Risk-sensitive foraging strategies of two spider populations. Ecology 68:887–99.CrossRefGoogle Scholar

Gilliam, J. F. (1982) Habitat use and competitive bottlenecks in sizestructured fish populations. Unpub. Ph.D. thesis, Michigan State University.Google Scholar

Gilliam, J. F. & Fraser, D. F. (1987) Habitat selection when foraging under predatio hazard: A model and a test with stream-dwelling minnows. Ecology 68:1856–62.CrossRefGoogle Scholar

Goodman, D. (1982) Optimal life histories, optimal notation and the value of reproductive value. American Naturalist 119:803–23.CrossRefGoogle Scholar

Gould, S. J. & Lewontin, R. C. (1979) The spandrels of San Marco and the Panglossian paradigm: A critique of the adaptationist programme. Proceedings of the Royal Society of London, Series B 205:581–98.Google Scholar

Grafen, A. (1984) Natural selection, kin selection and group selection. In: Behavioural ecology: An evolutionary approach. 2nd edition, ed. Krebs, J. R. & Davies, N. B.. Blackwell.Google Scholar

Grafen, A. (in press) On the uses of data on lifetime reproductive success. In: Reproductive success, ed. Clutton-Brock, T. H.. University of Chicago Press.Google Scholar

Green, R. F. (1984) Stopping rules for optimal foragers. American Naturalist 123:30–40.CrossRefGoogle Scholar

Green, R. F. (1987) Stochastic models of optimal foraging. In: Foraging behavior, ed. Kamil, A. C., Krebs, J. R. & Pulliam, H. R.. Plenum.Google Scholar

Greene, P. R. (1985) Running on flat turns: Experiments, theory, and applications. Journal of Biomechanical Engineering 107:96–103.CrossRefGoogle ScholarPubMed

Hamm, S. L. & Shettleworth, S. J. (in press) Risk aversion in pigeons. Journal of Experimental Psychology: Animal Behavior Processes.Google Scholar

Hanski, I. (1985) What does a shrew do in an energy crisis? In: Behavioural ecology: Ecological consequences of adaptive behaviour, ed. Sibley, R. M. & Smith, R. H.. Blackwell.Google Scholar

Heiner, R. A. (1983) The origin of predictable behavior. American Economic Review 73:560–95.Google Scholar

Heiner, R. A. (1985) Origin of predictable behavior: Further modeling and applications. American Economic Review 75:391–96.Google Scholar

Heiner, R. A. (1985a) Uncertainty, signal detection experiments, and modeling behavior. In: Economics as a process, ed. Langlois, R.. Cambridge University Press.Google Scholar

Heiner, R. A. (in press) The necessity of imperfect decisions. Journal of Economic Behavior and Organization.Google Scholar

Heiner, R. A. (in press a) Origin of predictable dynamic behavior. Journal of Economic Behavior and Organization.Google Scholar

Heiner, R. A. (forthcoming) Imperfect decisions, evolutionary stability and predictable behavior: The origin of rules over flexible optimizing. In: Quantitative analyses of behavior. Vol. 9, ed. Commons, M. L. & Herrnstein, R. J.. Behavioral Economics.Google Scholar

Heller, R. & Milinski, M. (1979) Optimal foraging of sticklebacks on swarming prey. Animal Behaviour 27:1127–41.CrossRefGoogle Scholar

Herrnstein, R. J. (1961) Relative and absolute strength of response as a function of reinforcement. Journal of the Experimental Analysis of Behavior 4:267–72.CrossRefGoogle ScholarPubMed

Herrnstein, R. J. (1964) Aperiodicity as a factor in choice. Journal of the Experimental Analysis of Behavior 7:179–82.CrossRefGoogle ScholarPubMed

Herrnstein, R. J. (1970) On the law of effect. Journal of the Experimental Analysis of Behavior 13:243–66.CrossRefGoogle ScholarPubMed

Herrnstein, R. J. & Heyman, G. M. (1979) Is matching compatible with reinforcement maximization on concurrent variable interval, variable ratio? Journal of the Experimental Analysis of Behavior 31:209–23.CrossRefGoogle ScholarPubMed

Herrnstein, R. J. & Vaughan, W. Jr. (1980) Melioration and behavioral allocation. In: Limits to action, ed. Staddon, J. E. R.. Academic Press.Google Scholar

Heyman, G. M. & Herrnstein, R. J. (1986) More on concurrent interval-ratio schedules. Journal of the Experimental Analysis of Behavior 46:331–51.CrossRefGoogle ScholarPubMed

Heyman, G. M. & Luce, R. D. (1979) Operant matching is not a logical consequence of maximizing reinforcement rate. Animal Learning and Behavior 7:133–40.CrossRefGoogle Scholar

Hodges, C. M. (1985) Bumble bee foraging: The threshold departure rule. Ecology 66:179–87.CrossRefGoogle Scholar

Hopfield, J. J. & Tank, D. W. (1985) “Neural” computation of decisions in optimization problems. Biological Cybernetics 52:141–52.CrossRefGoogle ScholarPubMed

Houston, A. I. (1980) Godzilla v. the creature from the black lagoon. In: The analysis of motivational processes, ed. Toates, F. M. & Halliday, T. R.. Academic Press.Google Scholar

Houston, A. I. (1983) Optimality theory and matching. Behaviour Analysis Letters 3:1–15.Google Scholar

Houston, A. I. (1986) The matching law applies to wagtails foraging in the wild. Journal of the Experimental Analysis of Behavior 45:15–18.CrossRefGoogle ScholarPubMed

Houston, A. I. (1987) The control of foraging decisions. In: Quantitative analyses of behavior. Vol. 6: Foraging, ed. Commons, M. L., Kacelnik, A., & Shettleworth, S. J.. Erlbaum.Google Scholar

Houston, A. I., Kacelnik, A. & McNamara, J. M. (1982) Some learning rules for acquiring information. In: Functional ontogeny, ed. McFarland, D. J.. Pitman.Google Scholar

Houston, A. I. & McNamara, J. M. (1981) How to maximize reward rate on two variable-interval paradigms. Journal of the Experimental Analysis of Behavior 35:367–96.CrossRefGoogle ScholarPubMed

Houston, A. I. & McNamara, J. M. (1982) A sequential approach to risk-taking. Animal Behaviour 30:1260–61.CrossRefGoogle Scholar

Houston, A. I. & McNamara, J. M. (1984) Imperfectly optimal animals: A correction. Behavioural Ecology and Sociobiology 15:61–64.CrossRefGoogle Scholar

Houston, A. I. & McNamara, J. M. (1985) The choice of two prey types that minimises the probability of starvation. Behavioural Ecology and Sociobiology 17:135–41.CrossRefGoogle Scholar

Houston, A. I. & McNamara, J. M. (1986) Evaluating the selection pressure on foraging decisions. In: Relevance of models and theories in ethology, ed. Campan, R. & Zayan, R.. Toulouse: Privat Press.Google Scholar

Houston, A. I. & McNamara, J. M. (1987) Singing to attract a mate – a stochastic dynamic game. Journal of Theoretical Biology 129:57–68.Google Scholar

Houston, A. I. & McNamara, J. M. (in press a) The value of food: Effects of open and closed economies. Animal Behaviour.Google Scholar

Houston, A. I. & McNamara, J. M. (in press b) Fighting for food: A dynamic version of the Hawk-Dove game. Evolutionary Ecology.Google Scholar

Houston, A. I., McNamara, J. M. & Sumida, B. H. (1987) Relative allocation can depend on schedule parameters when behavioral parameters are constant. Journal of the Experimental Analysis of Behavior 47:127–32.CrossRefGoogle ScholarPubMed

Houston, A. I. & Staddon, J. E. R. (1981) Optimality principles and behaviour: It's all for the best. Behavioral and Brain Sciences 4:395–96.CrossRefGoogle Scholar

Houston, A. I. & Sumida, B. H. (1987) Learning rules, matching and frequency dependence. Journal of Theoretical Biology 126:289–308.CrossRefGoogle Scholar

Houston, A. I., Sumida, B. H. & McNamara, J. M. (1987) Maximization of reinforcement rate on concurrent chains. Journal of the Experimental Analysis of Behavior 48:133–43.CrossRefGoogle ScholarPubMed

Howland, H. C. (1974) Optimal strategies for predator avoidance: The relative importance of speed and maneuverability. Journal of Theoretical Biology 47:333–50.CrossRefGoogle Scholar

Hursh, S. R. (1978) The economics of daily consumption controlling food and water-reinforced responding. Journal of the Experimental Analysis of Behavior 29:475–91.CrossRefGoogle ScholarPubMed

Hursh, S. R. (1980) Economic concepts for the analysis of behavior. Journal of the Experimental Analysis of Behavior 34:219–38.CrossRefGoogle ScholarPubMed

Hursh, S. R. (1984) Behavioral economics. Journal of the Experimental Analysis of Behavior 42:435–52.Google Scholar

Iwasa, Y., Higashi, M. & Yamamuia, N. (1981) Prey distribution as a factor determining the choice of optimal foraging strategy. American Naturalist 117:710–23.CrossRefGoogle Scholar

Iwasa, Y., Suzuki, Y. & Matsuda, H. (1984) Theory of oviposition strategy of parasitoids. I. Effect of mortality and limiting egg number. Theoretical Population Biology 26:205–27.CrossRefGoogle ScholarPubMed

Kagel, J. H., Green, L. & Caraco, T. (1986) When foragers discount the future: Constraint or adaptation? Animal Behaviour 34:217–83.CrossRefGoogle Scholar

Kagel, J. H., MacDonald, D. N., Battalio, R. C., White, S. & Green, L. (1986) Risk aversion in rats (Rattus norvegicus) under varying levels of resource availability. Journal of Comparative Psychology 100:95–100.CrossRefGoogle Scholar

Kamil, A. C. (1983) Optimal foraging theory and the psychology of learning. American Zoologist 23:291–302.CrossRefGoogle Scholar

Kamil, A. C., Peters, J. & Lindstrom, F. J. (1982) An ecological perspective on the study of the allocation of behavior. In: Quantitative analyses of behavior: Matching and maximizing accounts, ed. Commons, M. L., Herrnstein, R. J. & Rachlin, H.. Ballinger.Google Scholar

Kamil, A. C., Yoerg, S. I. & Clements, K. C. (in press) Rules to leave by: Patch departure in foraging blue jays. Animal Behaviour.Google Scholar

Karasov, W. H., Phan, D., Diamond, J. M. & Carpenter, F. L. (1986) Food passage and intestinal nutrient absorption in hummingbirds. Auk 103:453–64.CrossRefGoogle Scholar

Kareem, A. M. & Barnard, C. J. (1982) The importance of kinship and familiarity in social interactions between mice. Animal Behaviour 30:594–601.CrossRefGoogle Scholar

Karlin, S. & Taylor, H. M. (1975) A first course in stochastic processes. Academic Press.Google Scholar

Katz, P. L. (1974) A long-term approach to foraging optimization. American Naturalist 108:758–82.CrossRefGoogle Scholar

Killeen, P. (1968) On the measurement of reinforcement frequency in the study of preference. Journal of the Experimental Analysis of Behavior 11:263–69.Google Scholar

King, J. R. (1972) Adaptive periodic fat storage by birds. In: Proceedings of the sixteenth international ornithological congress, ed. Voous, K. H.. E. J. Brill.Google Scholar

King, J. R. & Murphy, M. E. (1985) Periods of nutritional stress in the annual cycles of endotherms: Fact or fiction? American Zoologist 25:955–64.CrossRefGoogle Scholar

Krebs, J. R. & Davies, N. B., eds. (1984) Behavioural ecology: An evolutionary approach, 2nd edition. Blackivell.Google Scholar

Krebs, J. R., Kacelnik, A. & Taylor, P. (1978) Test of optimal sampling by foraging tits. Nature 275:27–31.Google Scholar

Krebs, J. R., Stephens, D. W. & Sutherland, W. J. (1983) Perspectives in optimal foraging. In: Perspectives in ornithology, ed. Brush, A. H. & Clark, G. A. Jr. Cambridge University Press.Google Scholar

Kugler, P. N. & Turvey, M. T. (1987) Information, natural law, and the selfassembly of rhythmic movement. Erlbaum.Google Scholar

Lande, R. & Arnold, S. J. (1983) The measurement of selection on correlated characters. Evolution 37:1210–26.CrossRefGoogle ScholarPubMed

Larson, R. E. & Casti, J. L. (1982) Principles of dynamic programming. Part II: Advanced theory and applications. Marcel Dekker.Google Scholar

Lea, S. E. G. (1979) Foraging and reinforcement schedules in the pigeon: Optimal and non-optimal aspects of choice. Animal Behaviour 27:875–86.CrossRefGoogle Scholar

Lea, S. E. G. (1981) Correlation and continuity in foraging behaviour. In: Advances in analysis of behaviour, vol. 2, ed. Harzem, P. & Zeiler, M. H.. Wiley.Google Scholar

Lendrem, D. W. (1983) Predation risk and vigilance in the blue tit (Parus caeruleus). Behavioural Ecology and Sociobiology 14:9–13.CrossRefGoogle Scholar

Levine, R. (1966) The strategy of model building in population biology. American Scientist 54:421–31.Google Scholar

Lewontin, R. C. (1979) Fitness, survival and optimality. In: Analysis of ecological systems, ed. Hom, R. D., Stairs, E. R. & Mitchell, R. D.. OhioState University Press.Google Scholar

Leyhausen, P. (1979) Cat behavior. Garland.Google Scholar

Li, C. C. (1976) First course in population genetics. Boxwood Press.Google Scholar

Lima, S. L. (1983) Downy woodpecker foraging behavior: Foraging by expectation and energy intake rate. Oecologia 58:232–37.CrossRefGoogle ScholarPubMed

Lima, S. L. (1985) Maximizing feeding efficiency and minimizing time exposed to predators: A trade-off in the black-capped chickadee. Oecologia 66:60–7.CrossRefGoogle ScholarPubMed

Lima, S. L. (1986) Predation risk and unpredictable feeding conditions: Determinants of body mass in birds. Ecology 67:377–85.CrossRefGoogle Scholar

Logan, F. A. (1965) Decision making by rats: Uncertain outcome choices. Journal of Comparative and Physiological Psychology 59:246–51.CrossRefGoogle ScholarPubMed

Logue, A. W. & Chavarro, A. (1987) Effect on choice of absolute and relative values of reinforcer delay, amount, and frequency. Journal of Experimental Psychology: Animal Behavior Processes 13:280–91.Google Scholar

Logue, A. W. & Pena-Correal, T. E. (1984) Responding during reinforcement delay in a self-control paradigm. Journal of the Experimental Analysis of Behavior 41:267–77.Google Scholar

Logue, A. W. & Pena-Correal, T. E. (1985) The effect of food deprivation on self-control. Behavioural Processes 10:355–68.CrossRefGoogle ScholarPubMed

Logue, A. W., Rodriguez, M. L., Pena-Correal, T. E. & Mauro, B. C. (1984) Choice in a self-control paradigm: Quantification of experience-based differences. Journal of the Experimental Analysis of Behavior 41:53–67.CrossRefGoogle Scholar

Lorenz, K. Z. & Leyhausen, P. (1973) Motivation of human and animal behavior. Van Nostrand.Google Scholar

Lucas, J. (1983) The role of foraging time constraints and variable prey encounter in optimal diet choice. American Naturalist 122:191–209.CrossRefGoogle Scholar

Lucas, J. (1985) Time constraints and diet choice: Different predictions from different models. American Naturalist 126:680–705.CrossRefGoogle Scholar

Lucas, J. R. & Grafen, A. (1985) Partial prey consumption by ambush predators. Journal of Theoretical Biology 113:455–73.Google Scholar

Macevicz, S. & Oster, G. (1976) Modeling social insect populations. II: Optimal reproductive strategies in annual eusocial insect colonies. Behavioural Ecology and Sociobiology 1:265–82.CrossRefGoogle Scholar

Mangel, M. (1985) Decision and control in uncertain resource systems. Academic Press.Google Scholar

Mangel, M. (1987) Oviposition site selection and clutch size in insects. Journal of Mathematical Biology 25:1–22.CrossRefGoogle Scholar

Mangel, M. (submitted) A dynamic theory of diet selection,Google Scholar

Mangel, M.(unpublished) Dynamic foraging strategies of web-building spiders. Manuscript.Google Scholar

Mangel, M. & Clark, C. W. (1983) Uncertainty, search, and information in fisheries. Journal of the International Council for the Exploration of the Seas 41:93–103.Google Scholar

Mangel, M. & Clark, C. W. (1986) Towards a unified foraging theory. Ecology 67:1127–38.CrossRefGoogle Scholar

Marwine, A. & Collier, G. (1979) The rat at the waterhole. Journal of Comparative and Physiological Psychology 93:391–402.CrossRefGoogle Scholar

Masman, D. (1986) The annual cycle of the kestrel. Unpub. Ph.D. thesis, University of Groningen.Google Scholar

Maynard Smith, J. (1978) Optimization theory in evolution. Annual Review of Ecology and Systematics 9:31–56.CrossRefGoogle Scholar

Maynard Smith, J. (1982) Evolution and the theory of games. Cambridge University Press.CrossRefGoogle Scholar

Maynard Smith, J. (1984) Game theory and the evolution of behaviour. Behavioral and Brain Sciences 7:95–125.Google Scholar

Mazur, J. E. (1981) Optimization theory fails to predict performance of pigeons in a two-response situation. Science 241:823–25.CrossRefGoogle Scholar

Mazur, J. E. & Coe, D. (1987) Tests of transitivity in choices between fixed and variable reinforcer delays. Journal of the Experimental Analysis of Behavior 47:287–97.CrossRefGoogle ScholarPubMed

McCleery, R. H. (1977) On satiation curves. Animal Behaviour 25:1005–15.CrossRefGoogle Scholar

McCleery, R. H. (1978) Optimal behaviour sequences and decision making. In: Behavioral ecology (1st ed.), ed. Krebs, J. R. & Davies, N. B.. Blackwell.Google Scholar

McFarland, D. J. (1977) Decision making in animals. Nature 269:15–21.CrossRefGoogle Scholar

McFarland, D. J. & Wright, P. J. (1969) Water conservation by inhibition of food intake. Physiology and Behavior 4:95–99.CrossRefGoogle Scholar

McNamara, J. M. (1982) Optimal patch use in a stochastic environment. Theoretical Population Biology 21:269–88.CrossRefGoogle Scholar

McNamara, J. M. (1984) Control of a diffusion by switching between two drift-diffusion coefficient pairs. Society of Industrial and Applied Mathematics Journal of Control and Optimization 22:87–94.Google Scholar

McNamara, J. M. & Houston, A. I. (1980) The application of a statistical decision theory to animal behaviour. Journal of Theoretical Biology 85:673–90.CrossRefGoogle ScholarPubMed

McNamara, J. M. & Houston, A. I. (1982) Short-term behaviour and life-time fitness. In: Functional ontogeny, ed. McFarland, D. J.. Pitman.Google Scholar

McNamara, J. M. & Houston, A. I. (1983) Optimal responding on variable interval schedules. Behaviour Analysis Letters 3:157–70.Google Scholar

McNamara, J. M. & Houston, A. I. (1985) Optimal foraging and learning. Journal of Theoretical Biology 117:231–49.CrossRefGoogle Scholar

McNamara, J. M. & Houston, A. I. (1986) The common currency for behavioral decisions. American Naturalist 127:358–78.CrossRefGoogle Scholar

McNamara, J. M. & Houston, A. I. (1987) Foraging in patches: There's more to life than the marginal value theorem. In: Quantitative analyses of behavior. Vol. 6: Foraging, ed. Commons, M. L., Kacelnik, A. & Shettleworth, S. J.. Erlbaum.Google Scholar

McNamara, J. M. & Houston, A. I. (1987a) A general framework for understanding the effects of variability and interruptions on foraging behaviour. Acta Biotheorectica 36:3–22.CrossRefGoogle ScholarPubMed

McNamara, J. M. & Houston, A. I. (1987b) Partial preferences and foraging. Animal Behaviour 35:1084–99.CrossRefGoogle Scholar

McNamara, J. M. & Houston, A. I. (1987c) Starvation and predation as factors limiting population size. Ecology 68:1515–19.CrossRefGoogle Scholar

McNamara, J. M., Houston, A. I., Lima, S. L. & Mangel, (unpublished) Optimal daily routines of foraging for a small bird in winter.Google Scholar

McNamara, J. M., Mace, R. H. & Houston, A. I. (1987) Optimal daily routines of singing and foraging in a bird singing to attract a mate. Behavioural Ecology and Sociobiology 20:399–405.CrossRefGoogle Scholar

Metcalfe, N. B. & Furness, R. W. (1984) Changing priorities: The effect of pre-migratory fattening on the trade-off between foraging and vigilance. Behavioural Ecology and Sociobiology 15:203–6.CrossRefGoogle Scholar

Metcalfe, N. B., Huntingford, F. A. & Thorpe, J. E. (1987) The influence of predation risk on the feeding motivation and foraging strategy of juvenile Atlantic salmon. Animal Behaviour 35:901–11.CrossRefGoogle Scholar

Milinski, M. (1987) Tit for tat in sticklebacks and the evolution of cooperation. Nature 325:433–35.CrossRefGoogle ScholarPubMed

Milinski, M. & Heller, R. (1978) Influence of a predator on the optimal foraging behaviour of sticklebacks (Gasterosteus aculeatus). Nature 275:642–44.CrossRefGoogle Scholar

Misner, C., Thome, K. & Wheeler, J. A. (1973) Gravitation. W. H. Freeman.Google Scholar

Mitchell, B., McCowan, D. & Nicholson, I. A. (1976) Annual cycles of body weight and condition in Scottish red deer (Cervus elaphus). Journal of Zoology (London) 180:107–27.CrossRefGoogle Scholar

Morse, D. H. (1979) Prey capture by the crab spider Misumena calycina (Araneae: Thomisidae). Oecologia 39:309–19.CrossRefGoogle ScholarPubMed

Mrosovsky, N. & Powley, T. L. (1977) Set points for body weight and fat. Behavioral Biology 20:205–23.CrossRefGoogle ScholarPubMed

Mrosovsky, N. & Sherry, D. F. (1980) Animal anorexias. Science 207:837–42.CrossRefGoogle ScholarPubMed

Nagy, K. A. (1987) Field metabolic rate and food requirement scaling in mammals and birds. Ecological Monographs 57:111–28.CrossRefGoogle Scholar

Navarick, D. J. & Fantino, E. (1972) Transitivity as a property of choice. Journal of the Experimental Analysis of Behavior 18:389–401.CrossRefGoogle ScholarPubMed

Neuringer, A. J. (1969) Animals respond for food in the presence of free food. Science 166:399–401.CrossRefGoogle ScholarPubMed

Oaten, A. (1977) Optimal foraging in patches: A case for stochasticity. Theoretical Population Biology 12:263–85.CrossRefGoogle ScholarPubMed

Osborne, S. R. (1977) The free food (contra freeloading) phenomenon: A review and analysis. Animal Learning and Behavior 5:221–35.CrossRefGoogle Scholar

Oster, G. F. & Wilson, E. O. (1978) Caste and ecology in the social insects. Princeton University Press.Google ScholarPubMed

Parker, G. A. (1984) Evolutionarily stable strategies. In; Behavioural ecology (2nd ed.), ed. Krebs, J. R. & Davies, N. B.. Blackwell.Google Scholar

Peeke, H. V. S. & Veno, A. (1973) Stimulus specificity of habituated aggression in the stickleback. Behavioural Biology 8:427–32.CrossRefGoogle ScholarPubMed

Pierce, G. J. & Ollason, J. G. (1987) Eight reasons why optimal foraging theory is a complete waste of time. Oikos 49:111–18.CrossRefGoogle Scholar

Powers, W. T. (1973) Behavior: The control of perception. Aldine/Walter de Gruyter.Google Scholar

Pulliam, H. R. (1974) On the theory of optimal diets. American Naturalist 108:59–74.CrossRefGoogle Scholar

Pulliam, H. R. & Caraco, T. (1984) Living in groups: Is there an optimal group size? In: Behavioural ecology: An evolutionary approach (2nd ed), ed. Krebs, J. R. & Davies, N. B.. Blackwell.Google Scholar

Pulliam, H. R. & Millikan, C. C. (1982) Social organization in the nonreproductive season. In: Avian biology, vol. 6, ed. Farner, D. S. & King, J. R.. Academic Press.Google Scholar

Pyke, G. H. (1984) Optimal foraging theory: A critical review. Annual Review of Ecology and Systematics 15:523–75.CrossRefGoogle Scholar

Rachlin, H., Battalio, R. C., Kagel, J. H. & Green, L. (1981) Maximization theory in behavioral psychology. Behavioral and Brain Sciences 4:371–88.Google Scholar

Rachlin, H., Green, L., Kagel, J. H. & Battalio, R. C. (1976) Economic demand theory and psychological Studies of choice. In: The psychology of learning and motivation, vol. 10, ed. Bower, G. H.. Academic Press.Google Scholar

Rachlin, H., Kagel, J. H. & Green, L. (1980) Substitutability in time allocation. Psychological Review 87:355–74.CrossRefGoogle Scholar

Real, L. A. (1980) Fitness, uncertainty, and the role of diversification in evolution and behavior. American Naturalist 115:623–38.CrossRefGoogle Scholar

Real, L. A. & Caraco, T. (1986) Risk and foraging in stochastic environments: Theory and evidence. Annual Review of Ecology and Systematics 17:371–90.CrossRefGoogle Scholar

Rechten, C., Avery, M. & Stephens, A. (1983) Optimal prey selection: Why do great tits show partial preferences? Animal Behaviour 31:576–84.Google Scholar

Reeke, G. N. & Edelman, G. M. (1986) Recognition automata based on selective neural networks. In: Structure and dynamics of nucleic acids, proteins, and membranes, ed. Clementi, E. & Chin, S.. Plenum.Google Scholar

Reyer, U. & Westerterp, K. (1985) Parental energy expenditure: A proximate cause of helper recruitment in the pied kingfisher (Ceryle rudis). Behavioural Ecology and Sociobiology 17:363–69.CrossRefGoogle Scholar

Rijnsdorp, A., Daan, S. & Dijkstra, C. (1981) Hunting in the kestrel, Falco tinnunculus, and the adaptive significance of daily habits. Oecologia 50:391–406.CrossRefGoogle ScholarPubMed

Rodriguez, M. L. & Logue, A. W. (1986) Independence of the amount and delay ratios in the generalized matching law. Animal Learning and Behavior 14:29–37.CrossRefGoogle Scholar

Roitberg, B. & Mangel, M. (submitted) Dynamic information and host selection by a tephritid fruit fly.Google Scholar

Romanes, J. J. (1892) Darwin and after Darwin, vol. 1. Open Court.Google Scholar

Ross, S. (1983) Introduction to stochastic dynamic programming. Academic Press.Google Scholar

Rowland, W. J. & Sevenster, P. (1985) Sign stimuli in the threespine stickleback: A re-examination and extension of some classic experiments. Behaviour 93:241–57.Google Scholar

Rumelhart, D. E. & McClelland, J. L. (1986) Parallel distributed processing: Explorations in the microstructure of cognition. MIT Press.CrossRefGoogle Scholar

Sargent, R. C. (1985) Territoriality and reproductive trade-offs in the threespine stickleback. Behaviour 93:217–26.CrossRefGoogle Scholar

Savageau, M. (1976) Biochemical systems analysis. Addison-Wesley.Google Scholar

Schaffer, W. M. (1974) Selection for optimal life histories: The effects of age structure. Ecology 55:291–303.Google Scholar

Schaffer, W. M. (1983) The application of optimal control theory to the general life history problem. American Saturalist 121:418–31.CrossRefGoogle Scholar

Schaller, G. B. (1968) Hunting behaviour of the cheetah in the Serengeti National Park, Tanzania. East African Wildlife Journal 6:95–100.CrossRefGoogle Scholar

Schmalhausen, J. J. (1946) Faktorii evoluzii; teoria stabiliziriushevo otbora. Akademia Nauk SSK.Google Scholar

Schoener, T. W. (1971) Theory of feeding strategies. Annual Review of Ecology and Systematics 2:369–404.CrossRefGoogle Scholar

Schoener, T. W. (1986) Mechanistic approaches to community ecology: A new reductionism? American Zoologist 26:81–106.CrossRefGoogle Scholar

Scudo, F. M. (1987) Ethology, ecology, and philosophy. Rivista di Biologia – Biology Forum 80(2):252–56.Google Scholar

Shaw, R. E. & Alley, T. (1984) How to draw learning curves: Their use and justification. In: Issues in the ecological study of learning, ed. Johnston, T. & Pietrewicz, A.. Erlbaum.Google Scholar

Sherry, D. F. (1985) Food storage by birds and mammals. Advances in the Study of Behaviour 15:153–88.CrossRefGoogle Scholar

Sherry, D. F., Mrosovsky, N. & Hogan, J. A. (1980) Weight loss and anorexia during incubation in birds. Journal of Comparative and Physiological Psychology 94:89–98.CrossRefGoogle Scholar

Shimp, C. P. (1969) Optimal behavior in free-operant experiments. Psychological Review 76:97–112.Google Scholar

Sibly, R. M. & Calow, P. (1983) An integrated approach to life cycle evolution using selective landscapes. Journal of Theoretical Biology 102:527–47.CrossRefGoogle Scholar

Sibly, R. M., Calow, P. & Nichols, N. (1985) Are patterns of growth adaptive? Journal of Theoretical Biology 112:553–74.CrossRefGoogle ScholarPubMed

Sibly, R. M. & McCleery, R. (1985) Optimal decision rules for herring gulls. Animal Behaviour 33:445–65.CrossRefGoogle Scholar

Sibly, R. M. & McFarland, D. J. (1974) A state-space approach to motivation. In: Motivational control systems analysis, ed. McFartand, D. J.. Academic Press.Google Scholar

Sibly, R. M. & McFarland, D. J. (1976) On the fitness of behaviour sequences. American Naturalist 110:601–17.CrossRefGoogle Scholar

Sih, A. (1980) Optimal behavior: Can foragers balance two conflicting demands? Science 210:1041–43.CrossRefGoogle ScholarPubMed

Sih, A. (1982) Foraging strategies and the avoidance of predation by an aquatic insect, Notonecta hoffmanni. Ecology 63:786–96.CrossRefGoogle Scholar

Skinner, B. F. (1984) Methods and theories in the experimental analysis of behavior. Behavioral and Brain Sciences 7:511–41.CrossRefGoogle Scholar

Snyderman, M. (1983) Optimal prey selection: The effects of food deprivation. Behavioral Analysis Letters 3:359–69.Google Scholar

Staddon, J. E. R. (1979) Operant behavior as adaptation to constraint. Journal of Experimental Psychology: General 108:48–67.CrossRefGoogle Scholar

Staddon, J. E. R., Hinson, J. M. & Kram, R. (1981) Optimal choice. Journal of Experimental Analysis of Behavior 35:397–412.CrossRefGoogle ScholarPubMed

Staddon, J. E. R. & Reid, A. K. (1987) Adaptation to reward. In: Foraging behavior, ed. Kamil, A. C., Krebs, J. R. & Pulliam, H. R.. Plenum.Google Scholar

Stanley, B. V. & Wootton, R. J. (1986) Effects of ration and male density on the territoriality and nest-building of male threespined sticklebacks. Animal Behaviour 34:527–35.CrossRefGoogle Scholar

Stearns, S. C. (1976) Life-history tactics: A review of the ideas. Quarterly Review of Biology 51:3–47.Google Scholar

Stearns, S. C. (1977) The evolution of life-history traits: A critique of the theory and a review of the data. Annual Review of Ecology and Systematics 8:145–71.CrossRefGoogle Scholar

Stearns, S. C. (1980) A new view of life-history evolution. Oikos 35:266–81.CrossRefGoogle Scholar

Stearns, S. C. & Koella, J. C. (1986) The evolution of phenotypie plasticity in life-history traits: Predictions of reaction norms for age and size at maturity. Evolution 40:893–913.Google Scholar

Stenseth, N. C. (1986) Darwinian evolution in ecosystems: A survey of some ideas and difficulties together with some possible solutions. In: Complexity, language, and life: Mathematical approaches, ed. Casti, J. L. & Karlqvist, A.. Biomathematics, Springer Verlag.Google Scholar

Stenseth, N. C. & Maynard Smith, J. (1984) Coevolution in ecosystems; Red Queen evolution or stasis? Evolution 38:870–80.CrossRefGoogle ScholarPubMed

Stephens, D. W. (1981) The logic of risk-sensitive foraging preferences. Animal Behaviour 29:628–29.CrossRefGoogle Scholar

Stephens, D. W. & Chamov, E. L. (1982) Optimal foraging: Some simple stochastic models. Behavioural Ecology and Sodobiology 10:251–63.CrossRefGoogle Scholar

Stephens, D. W. & Krebs, J. R. (1986) Foraging theory. Princeton University Press.Google Scholar

Taylor, H. M., Gourley, R. S., Lawrence, C. E. & Kaplan, R. S. (1974) Natural selection of life history attributes: An analytical approach. Theoretical Population Biology 5:104–22.Google Scholar

Thompson, D. B. A. (1983) Prey assessment by plovers (Charadriidae): Net rate of energy intake and vulnerability to kleptoparasites. Animal Behaviour 31:1226–36.CrossRefGoogle Scholar

Timberlake, W., Gawley, D. J. & Lucas, G. A. (1987) Time horizons in rats foraging for food in temporally separated patches. Journal of Experimental Psychology: Animal Behavior Processes 13:302–9.Google ScholarPubMed

Timberlake, W. & Lucas, G. A. (in press) Behavior systems and learning: From misbehavior to general principles. In: Contemporary learning theories, ed. Klein, S. B. & Mowrer, R. R.. Erlbaum.Google Scholar

Tinbergen, J. M. (1981) Foraging decisions in starlings (Sturnus vulgaris L.). Ardea 69:1–67.Google Scholar

Tinbergen, N. (1951) The study of instinct. Clarendon Press.Google Scholar

Toates, F. M. (1979a) Water and energy in the interaction of thirst and hunger. In: Chemical influences on behaviour, ed. Brown, K. & Cooper, S. J.. Academic Press.Google Scholar

Toates, F. M. (1979b) Homeostasis and drinking. Behavioral and Brain Sciences 2:95–139.Google Scholar

Ukegbu, A. A. & Huntingford, F. A. (1987) Brood value and life expectations as determinants of parental investment in the threespined stickleback. Ethology.CrossRefGoogle Scholar

Valenstein, E. S. (1967) Selection of nutritive and non-nutritive solutions under different conditions of need. Journal of Comparative and Physiological Psychology 63:429–33.CrossRefGoogle Scholar

Vaughan, W. Jr. & Miller, H. L. Jr. (1984) Optimization versus responsestrength accounts of behavior. Journal of Experimental Analysis of Behavior 42:337–48.CrossRefGoogle ScholarPubMed

Vogel, P. (1976) Energy consumption of European and African shrews. Acta Theriologica 21:195–206.CrossRefGoogle Scholar

Wallace, R. F., Osborne, S., Norborg, J. & Fantino, E. (1973) Stimulus change contemporaneous with food presentation maintains responding in the presence of free food. Science 182:1038–39.CrossRefGoogle ScholarPubMed

Ward, P. (1977) Fat and protein reserves of starlings. Annual Report of the Institute of Terrestrial Ecology, Cambridge, England, pp. 54–56.Google Scholar

Weins, J. A. (1977) On competition and variable environments. American Scientist 65:590–97.Google Scholar

Werner, E. E. & Gilliam, J. F. (1984) The ontogenetic niche and species interactions in size-structured populations. Annual Review of Ecology and Systematics 15:393–425.Google Scholar

Werner, E. E., Gilliam, J. F., Hall, D. J. & Mittelbach, G. G. (1983) An experimental test of the effects of predation risk on habitat use in fish. Ecology 64:1540–48.CrossRefGoogle Scholar

Westerterp, K. R. & Drent, R. (1985) Energetic costs and energy-saving mechanisms in parental care of free-living passerine birds as determined by the D₂¹⁸O method. Acta XVIII Congressus Internationalis Ornithologici Moscow, pp. 392–98.Google Scholar

Westerterp, K. R., Gortmaker, W. & Wijngaarden, H. (1982) An energetic optimum in brood-raising in the starling (Sturnus vulgaris L.): An experimental study. Ardea 70:153–62.Google Scholar

Williams, B. K. & Nichols, J. D. (1984) Optimal timing in biological processes. American Naturalist 123:1–19.CrossRefGoogle Scholar

Williams, G. C. (1985) A defense of reductionism in evolutionary biology. In: Oxford surveys in evolutionary biology, vol. 2, ed. Dawkins, R. & Ridley, M.. Oxford University Press.Google Scholar

Williams, J. B. & Nagy, K. A. (1985) Water flux and energetics of nestling savannah sparrows in the field. Physiological Zoology 58:515–25.CrossRefGoogle Scholar

Winn, B. E. & Vestal, B. M. (1986) Kin recognition and choice of males by wild female house mice (Mus musculus). Journal of Comparative Psychology 100:72–75.Google Scholar

Winterhalder, B. (1986) Diet choice, risk, and food sharing in a stochastic environment. Journal of Anthropological Archaeology 5:369–92.CrossRefGoogle Scholar

Wolf, L. L. & Hainsworth, F. R. (1977) Temporal patterning of feeding by hummingbirds. Animal Behaviour 25:976–89.CrossRefGoogle Scholar

Yanai, J. & McCleam, G. E. (1972) Assortative mating in mice and the incest taboo. Nature 238:281–82.Google Scholar

Ydenberg, R. C. & Clark, C. W. (unpublished) Aerobic vs. anaerobic diving strategies of Western grebes (Aechmophorus occidentalis). Manuscript.Google Scholar

Ydenberg, R. C. & Dill, L. M. (1986) The economics of fleeing from predators. Advances in the Study of Behavior 16:229–49.CrossRefGoogle Scholar