Perhaps you should try some spelling variations:
ban thanh » ban hanh, ban hang
vu khach » vu khanh, vu khac, vay khach
hieu van » hieu va, thien van, lieu va
thanh ve » hanh ve, thanh va, thanh vien
thuc ban » thuoc ban, thuc dan, thu ban
nam thuc » nam thuoc, am thuc, nam thu
su triet » su viet, su tien, ve triet
cua tre » cua te, cuu tre, cua triet
y nang » ky nang, ly nang, v nang
o hoi » co hoi, o hoc, o hai
x hoi » xa hoi, x ho, 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: vu khach y nang ((x hoi) OR (o hoi)). hieu van nam thuc ban thanh ve ((cua tre) or (su triet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: vu khach y nang ((x hoi) OR (o hoi)). hieu van nam thuc ban thanh ve ((cua tre) OR (su triet)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "vu khach y nang ((x hoi) OR (o hoi)). hieu van nam thuc ban thanh ve ((cua tre) or (su triet))".
• Adding a wildcard symbol may retrieve word variants: vu khach y nang ((x hoi) OR (o hoi)). hieu van nam thuc ban thanh ve ((cua tre) or (su triet))*.