Perhaps you should try some spelling variations:
vie » viet, vien, view
viec » vietc, vienc, viewc, viet, vien
vienam" » vietnam", viennam", viewnam"
vientnam" » vietntnam", vienntnam", viewntnam"
vietnams" » viettnams", vientnams", viewtnams", vietnamese"
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 (vienam" or ((vientnam" OR vietnams") or vietnam"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: "(vie OR viec) (president OR residents) of (vienam" or ((vientnam" OR vietnams") or vietnam")).
• The words AND, OR and NOT may confuse the search; try adding quotes: "\"(vie or viec) (president or residents) of (vienam\" or ((vientnam\" OR vietnams\") or vietnam\"))".
• Removing quotes may allow a broader search: (vie or viec) (president or residents) of (vienam or ((vientnam OR vietnams ) or vietnam )).
• Adding a wildcard symbol may retrieve word variants: "(vie or viec) (president or residents) of (vienam" or ((vientnam" OR vietnams") or vietnam"))*.