The book is intended to serve as a textbook for B. A. /B. Sc. Hons. and Pass Course students of Indian Universities and abroad. It is also meant for the Engineering students and other professional competitive examinations such as IAS, IES, PCS etc. Pawan Kumar Jain (b. 1942) Fellow of the National Academy of Sciences (FNA Sc); formerly, Professor and Head, Department of Mathematics, University of Delhi