I feel extremely encouraged at the good response to this textbook. Looking upon the feed back received from its readers third edition of the book is being presented here.
In this edition number of solved and unsolved problems have been added in some of the chapters and a few new topics have also been added.
I wish to express my sincere thanks to Professors and students for their valuable suggestions and recommending the book to their students and friends.
I strongly feel that the book would prove to be further useful to students. I would be obliged forthe errors, omissions and suggestions brought to my notice for improvement of the book in its nextedition.