Acknowledgements
Sincerely thank you! The fact always shows that every success is always associated with the support and assistance from those around whether more or less, direct or indirect. During the time of the report, I - the author who conducted this research have received the attention, advice and support from my teachers, family and friends around.
With so deep gratitude, I gratefully give my acknowledgement to the teachers of Thuong Mai University and Toulon University for your motivation and enthusiasm with valuable knowledge during my period at school.
In particular, I would like to express my endless thanks and gratefulness to my supervisor Mr. Trinh Minh Duc for his dedicated instruction and guidance through each lesson and discussion on research topics. Thanks to those instructions, the thesis has been most sucessfully completed. Once again, I would like to express my sincere thanks to him.
Because of my limited knowledge, shortcomings may be unavoidable, any comments from teachers and classmates would be highly appreciated for a better thesis.