Perhaps you should try some spelling variations:
ban thanh » ban hanh, ban hang
van thanh » van tuan
hieu van » hieu va, thien van, lieu va
tu sach » thu sach, su sach, te sach
van cac » van hac, van cau, van bac
cac cac » cac cach, ca cac, cac bac
cua tre » cua te, cuu tre, cua triet
sach v » sach va, sach y, sach 2
v nang » va nang, vu nang, van nang
x hoi » xa hoi, o hoi, 5 hoi

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