Perhaps you should try some spelling variations:
hieu quan » lieu quan, thien quan, lien quan
hanh dai » hanh tai, hanh dao, vanh dai
nam thuc » nam thuoc, am thuc, nam thu
cua viet » ca viet, hoa viet, cua vat
hoa lang » hoa van
thuc va » thuc vat, thuc dan, thuc day
va hanh » van hanh, va thanh, va danh
tu sach » thu sach, su sach, te sach
ma hoi » mai hoi, xa hoi, ma hoa

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach ((hoa lang) or (hoa dan)) ma hoi. ((hieu quan) or (hieu qua)) nam thuc va hanh dai cua viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ((hoa lang) OR (hoa dan)) ma hoi. ((hieu quan) OR (hieu qua)) nam thuc va hanh dai cua viet.
• Adding a wildcard symbol may retrieve word variants: tu sach ((hoa lang) or (hoa dan)) ma hoi. ((hieu quan) or (hieu qua)) nam thuc va hanh dai cua viet*.