Perhaps you should try some spelling variations:
ban thanh » ban hanh, ban hang
tu sach » thu sach, su sach, te sach
vai cua » hai cua, lai cua, bai cua
dua ban » dia ban, cua ban, qua ban
sach ky » sac ky, sach y, sach ty
nang ma » tang ma, sang ma, nang cao
va cao » va cac, va co, va dao
va cam » va cham, va cac, va cai
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: tu sach ky nang ma hoi. hieu ((va cam) OR (va cao)) dua ban thanh ((vai cua) or (dai cua)) tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang ma hoi. hieu ((va cam) OR (va cao)) dua ban thanh ((vai cua) OR (dai cua)) tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang ma hoi. hieu ((va cam) OR (va cao)) dua ban thanh ((vai cua) or (dai cua)) tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang ma hoi. hieu ((va cam) OR (va cao)) dua ban thanh ((vai cua) or (dai cua)) tre*.