... I would like to express my deep gratitude to all my teachers at College of Foreign Languages, Vietnam National University-Hanoi for their valuable lectures. And their knowledge, their thoughtfulness ... knowledge, their thoughtfulness as well as their sympathy I will always appreciate.For the accomplishment of this study, I wish to show my sincere thanks to my supervisor Mr. Nguyễn Bàng, who has ... correction.I would like to acknowledge my debt to Assoc. Prof. Dr. Lê Hùng Tiến and the staff members of Postgraduate Department, College of Foreign Languages, VNU-Hanoi for their enthusiastic support.I...