The second and enlarged edition of the book is due to the enthusiastic response to the first edition by teachers and students alike. The present work incorporates many of the suggestions they have put forward.

The general plan, as described in the preface to the first edition, remains unchanged, except for the addition of two new chapters (6 and 7) on mathematical modelling in epidemiology and modelling the AIDS epidemic. These two chapters have been written by my old friend Professor K.B. Naidu of Sathya Sai Institute of Higher Learning, Bangalore. I am extremely grateful to him for writing these chapters in this book. Although I cannot here express individual thanks to all readers to whom I am indebted for useful critical comments, their communications stimulated me during the past nine years to think of improvements. I hope the new edition will make for easier reading and teaching from the book.

While preparing the second edition of this book, I have received assistance from many people. My heartfelt thanks go out to them all. Especially, I would like to thank TexAdel, Adelaide for meticulously typesetting the manuscript using LATEX and Anacleto Mernone for his excellent care and cooperation in producing the figures for the book. Finally, I wish to express my appreciation to my wife, Maya, for her personal support and encouragement during the preparation of the revised manuscript.