In the completion of this graduation paper, I constantly received useful
help, valuable advice, and encouragement from many of my teachers and
friends.
First and foremost, I would like to express my sincere thanks to all the
teachers in Hai Phong Private Uiversity (HPU) for their precious and useful
lectures which have enriched my knowledge and helped me achive the best
results as today.
In particular, I wish to expreess my deep gratitude to my supervisor:
Mrs Tran Thi Ngoc Lien, M.A who has given me useful advive, guidance and
supervison which clarified my point and helped to shape the idea of the paper.