Perhaps you should try some spelling variations:
thanh dai » thanh hai, thanh tai, thanh dat
hieu van » hieu va, thien van, lieu va
sach thu » sach thue, sach thieu, sach tham
dua ban » dia ban, qua ban, mua ban
van hac » van hoc, van ha, van hai
cua tre » cua te, cuu tre, cua triet
sach tu » cach tu, sach ty, sach uu
hang x » nang x, hoang xa, chang xu
x hoi » xa hoi, o hoi, x ho

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 tu) or (sach thu)) hang x hoi. hieu van hac ((dua ban) OR (cua ban)) thanh dai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te ((sach tu) OR (sach thu)) hang x hoi. hieu van hac ((dua ban) OR (cua ban)) thanh dai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te ((sach tu) or (sach thu)) hang x hoi. hieu van hac ((dua ban) OR (cua ban)) thanh dai cua tre".
• Adding a wildcard symbol may retrieve word variants: te ((sach tu) or (sach thu)) hang x hoi. hieu van hac ((dua ban) OR (cua ban)) thanh dai cua tre*.