In the process of doing my research paper, I have received a lot of
help, encouragement and experience from teachers and friends. Especially,
my graduation subject now is completed successfully thanks to all teachers’
support at Hai Phong Private University (HPU).
First of all, I would like to express my sincere thank to my supervisor
Mr. Mai Van Sao, MA who has generously given me invaluable assistance
and guidance. Without his help, this paper will not be successfully done.