ACKNOWLEDGEMENTS I would like to thank the many people who helped me accomplish this thesis. First, and foremost, I want Professor Svein Ottar Olsen, University of Tromso to know how much I appreciate his faithful guidance and unsurpassed expertise from the beginning to the end of the thesis writing. I especially would like to express my gratitude to him for his full enthusiastic supervisor. I could not have finished my thesis without his guidance and assistance. I also would like to thank Dr. Ho Huy Tuu, my external supervisor, Nha Trang University. Who commended and helped me in the data analyzing process. During the two years study programme at Nha Trang University, I am grateful to the financial supports of Norwegian government, the sch...