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"
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"))~.
• 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")).
• Removing quotes may allow a broader search: (vie or viec) (president or residents) of (viectnam or (vientnam OR vietnam )).
• Adding a wildcard symbol may retrieve word variants: "(vie or viec) (president or residents) of (viectnam" or (vientnam" OR vietnam"))*.