My heartiest gratitude goes to my father who left on the 13th March, 2005, whose love and inspiring messages put me up to this success. His insight visions of selfless sacrificed pushes me to go on. lt is distressful to celebrate when he is no more to rejoice along. This book is dedicated to His Memorial. I am deeply grateful to my beloved mother Lalengmawii Colney for her love, encouragement, and prayers all through the work. The study would not to its present form without her constant moral support and suggestions. Last, but not by any means least, I thank to Almighty God for giving me good health and strength, time and financial blessing to finish this manuscript. The views expressed in the book are entirely of the author and the others are duly cited in the text. Needless to say, that the omissions in the study are either of ignorance or of negligence and the mistake, the sole responsibility lies with the scholar.