Perhaps you should try some spelling variations:
ban thanh » ban hanh
hieu van » hieu va, thien van, lieu va
ban hang » ngan hang
van cac » van hac, van cau, van bac
cac dac » cac dan, cac dai, cac bac
tu sach » thu sach, su sach, te sach
ly hang » ly quang
ly nang » ky nang, ly vang, ly quang
cua tre » cua te, cuu tre, cua triet
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: tu sach ((ly nang) or (ly hang)) x hoi. hieu van cac dac ((ban thanh) OR (ban hang)) dai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ((ly nang) OR (ly hang)) x hoi. hieu van cac dac ((ban thanh) OR (ban hang)) dai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ((ly nang) or (ly hang)) x hoi. hieu van cac dac ((ban thanh) OR (ban hang)) dai cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ((ly nang) or (ly hang)) x hoi. hieu van cac dac ((ban thanh) OR (ban hang)) dai cua tre*.