Perhaps you should try some spelling variations:
ban thanh » ban hang
hieu van » hieu va, thien van, lieu va
ban hanh » ban hang
dang xay » dang van, van xay
van cac » van hac, van cau, van bac
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
lang ha » long ha
cua tre » cua te, cuu tre, cua triet
cac lo » cac lop, cac co, cac bo
va cua » va chua, via cua, ca cua

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

• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky ((lang ha) OR (dang xay)) hoi. hieu van cac lo ((ban thanh) OR (ban hanh)) va cua tre~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky ((lang ha) or (dang xay)) hoi. hieu van cac lo ((ban thanh) OR (ban hanh)) va cua tre~".
• Adding a wildcard symbol may retrieve word variants: tu sach ky ((lang ha) or (dang xay)) hoi. hieu van cac lo ((ban thanh) OR (ban hanh)) va cua tre*.