We thank the subjects of this study and the parents and other family members of the subjects for their patient co-operation. We are grateful to Mr. V. Gopal, who set the type on Electronic Typewriter for the entire book, and to Mr. S. B. Biswas, Manager, CIIL Printing Press and the other colleagues of ours in the CIIL Printing Press. We are indebted to Mr. Mir Nissar Hussain of the CIIL Library and Mr. Govindarajan, Librarian, All India Institute of Speech and Hearing, who helped us in locating various references. Mr. H. L. N. Bharati, Asst. Editor, CIIL, deserves a special mention and a word of gratitude. We are thankful to the authorities of the CIIL, in particular to Dr. D. P. Pattanayak, Director, CIIL, who accepted the manuscript for publication.

With love and admiration, we dedicate this book to Dr. N. Rathna, our mentor, teacher and doyen of Indian speech and hearing scientists.