Perhaps you should try some spelling variations:
hieu ban » hieu van, dieu ban, lieu ban
toc sach » hoc sach, doc sach, thuoc sach
ban hang » ngan hang
hang luc » nang luc, hang luan, hang truc
van hanh » van thanh, ban hanh, van anh
va hanh » va thanh, va danh, ban hanh
vai cua » dai cua, hai cua, lai cua
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: toc sach v nang ((x hoi) OR (x ho)). hieu ban hang luc ((va hanh) or (van hanh)) vai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach v nang ((x hoi) OR (x ho)). hieu ban hang luc ((va hanh) OR (van hanh)) vai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach v nang ((x hoi) OR (x ho)). hieu ban hang luc ((va hanh) or (van hanh)) vai cua tre".
• Adding a wildcard symbol may retrieve word variants: toc sach v nang ((x hoi) OR (x ho)). hieu ban hang luc ((va hanh) or (van hanh)) vai cua tre*.