Perhaps you should try some spelling variations:
hieu vien » hieu hien, thieu nien, hieu tieng
hieu viec » nhieu viec, hieu ve, sieu viet
sach tham » sach nha
ban hanh » ban hang
thuc ban » thuoc ban, thuc dan, thu ban
da thuc » dan thuc, dai thuc, dam thuc
sach ty » sach y, sach tu, sach thu
nang ma » tang ma, sang ma, nang cao
cua tre » cua te, cuu tre, cua triet
ma hoi » mai hoi, xa hoi, ma hoa
vi cua » vai cua, di cua

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

• Performing a fuzzy search may retrieve terms with similar spellings: su ((sach ty) or (sach tham)) nang ma hoi. ((hieu vien) or (hieu viec)) da thuc ban hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sach ty) OR (sach tham)) nang ma hoi. ((hieu vien) OR (hieu viec)) da thuc ban hanh vi cua tre.
• Adding a wildcard symbol may retrieve word variants: su ((sach ty) or (sach tham)) nang ma hoi. ((hieu vien) or (hieu viec)) da thuc ban hanh vi cua tre*.