Perhaps you should try some spelling variations:
ban thanh » ban hanh, ban hang
nam thuc » nam thuoc, am thuc, nam thu
hieu van » hieu va, thien van, lieu va
thuc ban » thuoc ban, thuc dan, thu ban
thanh di » thanh doi, thanh de, thanh do
cau treo » cau theo, cau tren, cau triet
cuu tre » cua tre, cau tren
su sac » su sach, su cac, su xac
sac ky » cac ky, sai ky
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 sac ky nang ((x hoi) or (x ho)). hieu van nam thuc ban thanh di ((cuu tre) or (cau treo))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sac ky nang ((x hoi) OR (x ho)). hieu van nam thuc ban thanh di ((cuu tre) OR (cau treo)).
• Adding a wildcard symbol may retrieve word variants: su sac ky nang ((x hoi) or (x ho)). hieu van nam thuc ban thanh di ((cuu tre) or (cau treo))*.