I am grateful to ALLAH who blessed me with courage and supportive people around me who stood with me in times of difficulty. I dedicate this book to my loving parents and my supportive wife. I also give thanks to my mentors Prof Tariq Mansoor & Prof Naheed Bano who guided me in thick and thin and gave a proper channel to all my energies. I am also thankful to my dear friends without whom this work may not have been possible. Last but not the least I am thankful to the readers who made this book a success. Regards Dr. Manzoor Ahmad