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 tu
thanh le » thinh le, thanh ve, thanh de
te sach » toc sach
sach ky » sac ky, sach y, sach ty
cua tre » cua te, cuu tre, cua triet
le cua » ly cua
x hoi » xa hoi, o hoi, x ho

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

• Performing a fuzzy search may retrieve terms with similar spellings: te sach ky nang x hoi. hieu van ((nam thuc) or (nam thu)) ban thanh le cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sach ky nang x hoi. hieu van ((nam thuc) OR (nam thu)) ban thanh le cua tre.
• Adding a wildcard symbol may retrieve word variants: te sach ky nang x hoi. hieu van ((nam thuc) or (nam thu)) ban thanh le cua tre*.