Perhaps you should try some spelling variations:
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
hieu ve » hieu va, hieu van
nang ma » tang ma, sang ma, nang cao
cua tre » cua te, cuu tre, cua triet
ma hoi » mai hoi, xa hoi, ma hoa
cac tu » cac thu, cach tu, cac du
dau vi » dau ve, dau va, dat vi
lau va » dau va

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach ky nang ma hoi. ((hieu ve) or (hieu qua)) cac tu va ((dau vi) or (lau va)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang ma hoi. ((hieu ve) OR (hieu qua)) cac tu va ((dau vi) OR (lau va)) cua tre.
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang ma hoi. ((hieu ve) or (hieu qua)) cac tu va ((dau vi) or (lau va)) cua tre*.