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
cam duc » cam xuc, cao duc, pham duc
vai cua » dai cua, hai cua, lai cua
tu sach » thu sach, su sach, te sach
van cam » van nam, van lam, van cau
sach ky » sac ky, sach y, sach ty
dang xa » lang xa, dang ha, dang va
cua tre » cua te, cuu tre, cua triet

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 ((dang xa) or (dang xay)) hoi. hieu van cam duc ((ban thanh) or (ban hanh)) vai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky ((dang xa) OR (dang xay)) hoi. hieu van cam duc ((ban thanh) OR (ban hanh)) vai cua tre.
• Adding a wildcard symbol may retrieve word variants: tu sach ky ((dang xa) or (dang xay)) hoi. hieu van cam duc ((ban thanh) or (ban hanh)) vai cua tre*.