Perhaps you should try some spelling variations:
ban thanh » ban hanh, ban hang
thanh doi » thanh loi, thanh moi, thanh do
hieu van » hieu va, thien van, lieu va
cau treo » cau theo, cau tren, cau triet
su sach » so sach, vu sach
sach ky » sac ky, sach y, sach ty
nam xuc » cam xuc, nam xua, nam thuc
xuc ban » duc ban, cuc ban, quoc ban
cuu tre » cua tre, cau tren
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: su sach ky nang ((x hoi) or (x ho)). hieu van nam xuc ban thanh doi ((cuu tre) or (cau treo))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky nang ((x hoi) OR (x ho)). hieu van nam xuc ban thanh doi ((cuu tre) OR (cau treo)).
• Adding a wildcard symbol may retrieve word variants: su sach ky nang ((x hoi) or (x ho)). hieu van nam xuc ban thanh doi ((cuu tre) or (cau treo))*.