To Padmashri N.D. Sundaravadivelu, the emient Vice-Chancellor of the University of Madras, my sincere thanks are due for sanctioning the publication of my doctoral thesis in the University with the grant made available by the University Grants Commission.

I am grateful to the respected Vice-Chancellor Padmashri N.D. Sundaravadivelu for his foreword to this book.

To Prof. K. D. Thirunavukkarasu, Thiru R. Subramanian, Thiru A.A. Manavalan, Thiru N. Ramamoorthy, Thiru V. Subramaniam and Thiru Rabi Singh, my thanks are due for their interest in the work and for having helped me with the proof corrections.

My wife Mrs. Jaya Meenakshisundaram and daughter. Miss Manonmani have been of immense help to me in this regard. I am also grateful to them.

I express my gratitude to Messrs. Rathnam Press for having executed the printing neatly.