Published online by Cambridge University Press: 14 July 2016
In this article, we generalize results by Dimitrov and Khalil (1990), Khalil et al. (1991), and van Harn and Steutel (1991) and obtain some characterizations of the exponential and geometric laws.
Support for this research was provided in part by the National Science Council of the Republic of China, Grant No. NSC 80–0208-M1 10–06.