Perhaps you should try some spelling variations:
chat thuc » thuat thuc, nhan thuc, chat thai
hieu van » thien van, lieu va
hanh vai » hanh vi, hanh va, hanh tai
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
sach ty » sach y, sach tu, sach thu
tang ma » mang may, tang van
ty tang » tay tang, ty xang, ty hang
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 ty tang ma hoi. ((((hieu ve) OR (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 ty tang ma hoi. ((((hieu ve) OR (hieu va))) OR (hieu van)) chat thuc va hanh vai va thiet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sach ty tang ma hoi. ((((hieu ve) OR (hieu va))) or (hieu van)) chat thuc va hanh vai va thiet".
• Adding a wildcard symbol may retrieve word variants: te sach ty tang ma hoi. ((((hieu ve) OR (hieu va))) or (hieu van)) chat thuc va hanh vai va thiet*.