THE THESIS'S STRUCTURE The main part of the thesis is 134 pages long, including the following sections: Introduction: 2 pages Chapter 1 - Overview: 37 pages Chapter 2 - Subjects and methods applied to the study: 25 pages Chapter 3 - Results reached of the study: 36 pages Chapter 4 - Discussion: 31 pages Conclusion and recommendations: 2 pages The thesis refers to 184 documents, including 35 Vietnamese documents and 149 English ones.