Perhaps you should try some spelling variations:
van thanh » ban thanh, van tuan
sach thu » sach thue, sach thieu, sach tham
thu hang » thi hang, thuc hanh, thu huong
so sach » so sanh, bo sach, co sach
cao hoi » cau hoi, cao hoc, tao hoi
qua cac » cua cac
cac xuc » cam xuc, cac nuoc, chat xuc
cua tre » cua te, cuu tre, cua triet
co hoi » co hoc, co loi
di cua » dai cua, doi cua, de cua

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

• Performing a fuzzy search may retrieve terms with similar spellings: so sach thu hang ((cao hoi) or (co hoi)). hieu qua cac xuc ((van ban) or (van thanh)) di cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach thu hang ((cao hoi) OR (co hoi)). hieu qua cac xuc ((van ban) OR (van thanh)) di cua tre.
• Adding a wildcard symbol may retrieve word variants: so sach thu hang ((cao hoi) or (co hoi)). hieu qua cac xuc ((van ban) or (van thanh)) di cua tre*.