Perhaps you should try some spelling variations:
hieu quan » lieu quan, thien quan, lien quan
chat thuc » thuat thuc, nhan thuc, chat thai
hanh vai » hanh vi, hanh va, hanh tai
te sach » toc sach
tu tang » tuc tang, tu trang, tu tong
tang ma » mang may, tang van
hieu ve » hieu va, hieu van
va hanh » van hanh, va thanh, va danh
sach tu » sach thu, cach tu, sach ty
thuc va » thuc vat, thuc dan, thuc day
ma hoi » mai hoi, xa hoi, ma hoa
vai va » mai va, dai va, hai va
thiet » thieu

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

• Performing a fuzzy search may retrieve terms with similar spellings: te sach tu tang ma hoi. ((((hieu ve) or (hieu qua))) or (hieu quan)) chat thuc va hanh vai va thiet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sach tu tang ma hoi. ((((hieu ve) OR (hieu qua))) OR (hieu quan)) chat thuc va hanh vai va thiet.
• Adding a wildcard symbol may retrieve word variants: te sach tu tang ma hoi. ((((hieu ve) or (hieu qua))) or (hieu quan)) chat thuc va hanh vai va thiet*.