Perhaps you should try some spelling variations:
ban thanh » ban hanh, ban hang
hieu van » hieu va, thien van, lieu va
nam thuc » nam thuoc, am thuc, nam thu
thuc ban » thuoc ban, thuc dan, thu ban
thanh vi » hanh vi, thanh va, thanh ve
va triet » va thiet, ve triet, cua triet
va trien » va truyen, va thiet, va tuyen
cua tre » cua te, cuu tre, cua triet
y nang » ky nang, ly nang, v nang
nang o » nang co, nang ho, nang ro
o hoi » co hoi, o hoc, o hai
khach » khac, khanh

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

• Performing a fuzzy search may retrieve terms with similar spellings: vay khach y nang o hoi. hieu van nam thuc ban thanh vi ((cua tre) or (((va triet) OR (va trien))))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: vay khach y nang o hoi. hieu van nam thuc ban thanh vi ((cua tre) OR (((va triet) OR (va trien))))*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "vay khach y nang o hoi. hieu van nam thuc ban thanh vi ((cua tre) or (((va triet) OR (va trien))))*".