Perhaps you should try some spelling variations:
ban thanh » ban hang
hieu van » hieu va, thien van, lieu va
lam duoc » nam duoc, luat duoc, lam thuoc
ban hanh » ban hang
van lam » van nam
sach ky » sach y, sach ty, sach kem
cua tre » cua te, cuu tre, cua triet
nang o » nang co, nang ho, nang ro
sac ky » cac ky, sai ky
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: tu ((sach ky) or (sac ky)) nang o hoi. hieu van lam duoc ((ban thanh) or (ban hanh)) dai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sach ky) OR (sac ky)) nang o hoi. hieu van lam duoc ((ban thanh) OR (ban hanh)) dai cua tre.
• Adding a wildcard symbol may retrieve word variants: tu ((sach ky) or (sac ky)) nang o hoi. hieu van lam duoc ((ban thanh) or (ban hanh)) dai cua tre*.