Perhaps you should try some spelling variations:
chat thuc » thuat thuc, nhan thuc, chat thai
hanh vai » hanh vi, hanh va, hanh tai
hieu van » thien van, lieu va, hieu ve
te sach » toc sach
va hanh » van hanh, va thanh, va danh
thuc va » thuc vat, thuc dan, thuc day
hieu va » lieu va, hieu qua
ma hoi » mai hoi, xa hoi, ma hoa
7 tang » 6 tang
5 tang » 6 tang
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 ((5 tang) or (7 tang)) ma hoi. ((hieu va) or (hieu van)) chat thuc va hanh vai va thiet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sach ((5 tang) OR (7 tang)) ma hoi. ((hieu va) OR (hieu van)) chat thuc va hanh vai va thiet.
• Adding a wildcard symbol may retrieve word variants: te sach ((5 tang) or (7 tang)) ma hoi. ((hieu va) or (hieu van)) chat thuc va hanh vai va thiet*.