Perhaps you should try some spelling variations:
vie » viet, vien, view
viec » vietc, vienc, viewc, viet, vien
viettnam" » vietttnam", vienttnam", viewttnam", vietnam", vienam"
vientnam" » vietntnam", vienntnam", viewntnam", vietnam", vienam"
vietnams" » viettnams", vientnams", viewtnams", vietnam", vietnamese", vienam"
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 (viettnam" or ((vientnam" or vietnams") or viettnam"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: "(vie OR viec) (president OR residents) of (viettnam" or ((vientnam" OR vietnams") or viettnam")).
• Removing quotes may allow a broader search: (vie or viec) (president or residents) of (viettnam or ((vientnam or vietnams ) or viettnam )).
• Adding a wildcard symbol may retrieve word variants: "(vie or viec) (president or residents) of (viettnam" or ((vientnam" or vietnams") or viettnam"))*.