Perhaps you should try some spelling variations:
te sach » toc sach
doan vi » doan va, don vi, doan thi
sach ky » sac ky, sach y, sach ty
hieu ve » hieu van
hieu va » lieu va, hieu qua
tang ma » mang may, tang van
ky tang » ky nang, ky dang, kho tang
cua tre » cua te, cuu tre, cua triet
ma hoi » mai hoi, xa hoi, ma hoa
tro va » tao va, tho va, tro ba
dan vi » don vi, dan va, gan vi

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 ve) or (hieu va)) cac tro va ((dan vi) OR (doan vi)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sach ky tang ma hoi. ((hieu ve) OR (hieu va)) cac tro va ((dan vi) OR (doan vi)) cua tre*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sach ky tang ma hoi. ((hieu ve) or (hieu va)) cac tro va ((dan vi) OR (doan vi)) cua tre*".