Perhaps you should try some spelling variations:
chat thuc » thuat thuc, nhan thuc, chat huu
hanh vai » hanh vi, hanh va, hanh tai
hieu van » thien van, lieu va, hieu ve
te sach » toc sach
ky tang » ky nang, ky dang, kho tang
tang ma » mang may, tang van
hieu va » lieu va, hieu qua
va hanh » van hanh, va thanh, va danh
sach ky » sac ky, sach y, sach ty
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 ky tang ma hoi. ((hieu va) or (hieu van)) ((chat thuc) OR (chat thai)) va hanh vai va thiet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sach ky tang ma hoi. ((hieu va) OR (hieu van)) ((chat thuc) OR (chat thai)) va hanh vai va thiet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sach ky tang ma hoi. ((hieu va) or (hieu van)) ((chat thuc) OR (chat thai)) va hanh vai va thiet".
• Adding a wildcard symbol may retrieve word variants: te sach ky tang ma hoi. ((hieu va) or (hieu van)) ((chat thuc) OR (chat thai)) va hanh vai va thiet*.