Perhaps you should try some spelling variations:
ban thanh » ban hanh, ban hang
hieu van » hieu va, thien van, lieu va
su sach » so sach, vu sach
dua ban » dia ban, cua ban, qua ban
lai cua » dai cua, hai cua, lai chau
vai cua » dai cua, hai cua, bai cua
van bay » van ban, van bao, van bac
bay dua » cay dua, chay dua
sach ky » sac ky, sach y, sach ty
mai hoi » mai khoi, dai hoi, lai hoi

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 ky nang ((mai hoi) or (ma hoa)). hieu van bay dua ban thanh ((vai cua) OR (lai cua)) tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky nang ((mai hoi) OR (ma hoa)). hieu van bay dua ban thanh ((vai cua) OR (lai cua)) tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ky nang ((mai hoi) or (ma hoa)). hieu van bay dua ban thanh ((vai cua) OR (lai cua)) tre".
• Adding a wildcard symbol may retrieve word variants: su sach ky nang ((mai hoi) or (ma hoa)). hieu van bay dua ban thanh ((vai cua) OR (lai cua)) tre*.