Perhaps you should try some spelling variations:
ban thanh » ban hanh, ban hang
hieu van » hieu va, thien van, lieu va
vu sach » vu bach, su sach, vu khach
sach ky » sac ky, sach y, sach ty
va dinh » van dinh, va kinh, va tinh
su viet » so viet
dam tu » nam tu, cam tu, dam thuc
tam tu » nam tu, cam tu, tam thuc
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 sach ky nang x ho. hieu van ((dam tu) or (tam tu)) ((ban thanh) or (va dinh)) ki su viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: vu sach ky nang x ho. hieu van ((dam tu) OR (tam tu)) ((ban thanh) OR (va dinh)) ki su viet.
• Adding a wildcard symbol may retrieve word variants: vu sach ky nang x ho. hieu van ((dam tu) or (tam tu)) ((ban thanh) or (va dinh)) ki su viet*.