Perhaps you should try some spelling variations:
sach thu » sach thue, sach thieu, sach tham
ban hanh » ban hang
tu sach » thu sach, su sach, te sach
thu nao » thu bao, thu lao, thu nam
van cam » van nam, van lam, van dam
van cau » van dau, van hau, van chat
cac ban » cac dan, cac van, can ban
cua tre » cua te, cuu tre, cua triet
va hoi » xa hoi, va hoc, va 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: tu sach thu nao ((va hoi) or (van hoa)). thien ((van cam) or (van cau)) cac ban hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach thu nao ((va hoi) OR (van hoa)). thien ((van cam) OR (van cau)) cac ban hanh vi cua tre.
• Adding a wildcard symbol may retrieve word variants: tu sach thu nao ((va hoi) or (van hoa)). thien ((van cam) or (van cau)) cac ban hanh vi cua tre*.