Perhaps you should try some spelling variations:
ban thanh » ban hanh
cua viet » ca viet, hoa viet, cua vat
ban hang » ngan hang
hieu van » hieu va, thien van, lieu va
tang xa » trang xa, tang ma, lang xa
ky tang » ky nang, ky dang, kho tang
so sach » so sanh, bo sach, co sach
su sach » vu sach
van am » van nam, van lam, van dam
vi cua » vai cua, di cua

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((su sach) or (so sach)) ky tang xa hoi. hieu van am thuc ((ban thanh) OR (ban hang)) vi cua viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((su sach) OR (so sach)) ky tang xa hoi. hieu van am thuc ((ban thanh) OR (ban hang)) vi cua viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((su sach) or (so sach)) ky tang xa hoi. hieu van am thuc ((ban thanh) OR (ban hang)) vi cua viet".
• Adding a wildcard symbol may retrieve word variants: ((su sach) or (so sach)) ky tang xa hoi. hieu van am thuc ((ban thanh) OR (ban hang)) vi cua viet*.