Perhaps you should try some spelling variations:
vu khach » vu khanh, vu khac, vay khach
nam thuc » nam thuoc, am thuc, nam thu
ca viet » va viet, hoa viet, san viet
va hanh » van hanh, va thanh, va danh
thuc va » thuc vat, thuc dan, thuc day
hieu va » lieu va, hieu qua
mai hoi » mai khoi, dai hoi, lai hoi
ky tang » ky nang, ky dang, kho tang
ky sang » ky nang, ky dang, duy sang
co viet » so viet, o viet, hoc viet
va nam » van nam, ha nam, va nay

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

• Performing a fuzzy search may retrieve terms with similar spellings: vu khach ((ky sang) OR (ky tang)) mai hoi. hieu va nam thuc va hanh vi ((ca viet) or (co viet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: vu khach ((ky sang) OR (ky tang)) mai hoi. hieu va nam thuc va hanh vi ((ca viet) OR (co viet)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "vu khach ((ky sang) OR (ky tang)) mai hoi. hieu va nam thuc va hanh vi ((ca viet) or (co viet))".
• Adding a wildcard symbol may retrieve word variants: vu khach ((ky sang) OR (ky tang)) mai hoi. hieu va nam thuc va hanh vi ((ca viet) or (co viet))*.