Perhaps you should try some spelling variations:
vie » viet, vien, view
viec » vietc, vienc, viewc, viet, vien
viectnam" » vietctnam", vienctnam", viewctnam", viettnam", vientnam", vienam", vietnams"
vientnam" » vietntnam", vienntnam", viewntnam", vienam", vietnams"
vietnam" » viettnam", vientnam", viewtnam"
viettnam" » vietttnam", vienttnam", viewttnam", vienam", vietnams"
president » resident, present

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: "(vie or viec) (president or residents) of (viectnam" or (vientnam" or (vietnam" OR viettnam")))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: "(vie OR viec) (president OR residents) of (viectnam" or (vientnam" OR (vietnam" OR viettnam"))).
• Removing quotes may allow a broader search: (vie or viec) (president or residents) of (viectnam or (vientnam or (vietnam OR viettnam ))).
• Adding a wildcard symbol may retrieve word variants: "(vie or viec) (president or residents) of (viectnam" or (vientnam" or (vietnam" OR viettnam")))*.