Trung NL, Hung NV. MODELS FOR ENHANCING THE FOREIGN LANGUAGE PROFICIENCY OF OFFICIALS AND OFFICERS IN THE CUSTOMS, FOREIGN RELATIONS, TOURISM AND BORDER GUARDS SECTORS IN VIETNAM’S NORTHERN BORDER REGIONS: FROM PRACTICE TO KEY PRINCIPLES. JFS [Internet]. 2018 Dec. 3 [cited 2024 Nov. 21];34(6). Available from: https://jfs.ulis.vnu.edu.vn/index.php/fs/article/view/4331