Perhaps you should try some spelling variations:
ban thanh » ban hang
hieu van » hieu va, thien van, lieu va
ban hanh » ban hang
so sach » so sanh, bo sach, co sach
sach ky » sac ky, sach y, sach ty
nang ma » tang ma, sang ma, nang cao
nam qua » nam quan, nam cua, nam mua
vai cua » dai cua, hai cua, bai cua
lai cua » dai cua, hai cua, lai chau
ma hoi » mai hoi, xa hoi, ma hoa

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

• Performing a fuzzy search may retrieve terms with similar spellings: so sach ky nang ma hoi. hieu van nam qua ((ban thanh) OR (ban hanh)) ((vai cua) or (lai cua)) tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach ky nang ma hoi. hieu van nam qua ((ban thanh) OR (ban hanh)) ((vai cua) OR (lai cua)) tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach ky nang ma hoi. hieu van nam qua ((ban thanh) OR (ban hanh)) ((vai cua) or (lai cua)) tre".
• Adding a wildcard symbol may retrieve word variants: so sach ky nang ma hoi. hieu van nam qua ((ban thanh) OR (ban hanh)) ((vai cua) or (lai cua)) tre*.