This book provides a comprehensive course of subject. The book is written primarily for university teachers, college lectures, research scholars students of our country. The special features of this book are :
    (l) The book takes full advantage of the clarity and consistency of modern terminology.
    (2) The development of the chapters is logical and the preparation of each new idea is based on the preceding martial.
    (3) The clearly developed textual explanations are followed in appropriate solved examples.
    (4) The book reflects the author's conviction that one learns by own self.
    (5) A proper balance between theory and practice is maintained in every chapter.
    I hope that present book will be found to be more useful to readers. I take opportunity to express my sincere gratitude to Prof. Tiwari Gandhi for his inspiration and constant encouragement.
    Every effort has been made to avoid printing errors, though some might have exept inadvertently. I shall be obliged if any such errors are brought to my notice. Suggestions for improvement in the next addition is always welcome.