Perhaps you should try some spelling variations:
thanh toan » thanh hoa, thanh san, tinh toan
thanh van » thanh san, thanh phan, thanh nhan
hieu van » hieu va, thien van, lieu va
su sach » so sach, vu sach
sach ky » sac ky, sach y, sach ty
nam duc » nam duoc, pham duc, nam thuc
duc ban » duc tan, duc van, dua ban
cua tre » cua te, cuu tre, cua triet
x hoi » xa hoi, x ho, 5 hoi
o hoi » co hoi, o hoc, o hai

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: su sach ky nang ((x hoi) or (o hoi)). hieu van nam duc ban ((thanh van) OR (thanh toan)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky nang ((x hoi) OR (o hoi)). hieu van nam duc ban ((thanh van) OR (thanh toan)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ky nang ((x hoi) or (o hoi)). hieu van nam duc ban ((thanh van) OR (thanh toan)) cua tre".
• Adding a wildcard symbol may retrieve word variants: su sach ky nang ((x hoi) or (o hoi)). hieu van nam duc ban ((thanh van) OR (thanh toan)) cua tre*.