Perhaps you should try some spelling variations:
ban thanh » ban hanh, ban hang
va thanh » gia thanh, va tinh, le thanh
cua viet » ca viet, hoa viet, cua vat
sach tu » sach thu, sach ty, sach uu
cach tu » cach thuc
cao hoi » cau hoi, co hoi, cao hoc
hieu va » lieu va, hieu qua
cac duc » cac du, cao duc, cac dac
vai cua » dai cua, hai cua, lai 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 tu) or (cach tu)) nang cao hoi. hieu va cac duc ((va thanh) OR (ban thanh)) vai cua viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sach tu) OR (cach tu)) nang cao hoi. hieu va cac duc ((va thanh) OR (ban thanh)) vai cua viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su ((sach tu) or (cach tu)) nang cao hoi. hieu va cac duc ((va thanh) OR (ban thanh)) vai cua viet".
• Adding a wildcard symbol may retrieve word variants: su ((sach tu) or (cach tu)) nang cao hoi. hieu va cac duc ((va thanh) OR (ban thanh)) vai cua viet*.