Perhaps you should try some spelling variations:
ban thanh » ban hanh, ban hang
hieu van » hieu va, thien van, lieu va
su viet » so viet
vu sac » vu sach, vu san, va sac
sac ky » cac ky, sai ky
nam tu » nam thu, nam thuc
va dan » ca dan, va dao, va dau
ki su » ky su

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

• Performing a fuzzy search may retrieve terms with similar spellings: vu sac ky nang x ho. hieu van nam tu ((ban thanh) or (va dan)) ki su viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: vu sac ky nang x ho. hieu van nam tu ((ban thanh) OR (va dan)) ki su viet.
• Adding a wildcard symbol may retrieve word variants: vu sac ky nang x ho. hieu van nam tu ((ban thanh) or (va dan)) ki su viet*.