Perhaps you should try some spelling variations:
ban hang » ngan hang
so sach » so sanh, bo sach, co sach
hieu va » lieu va
cua tre » cua te, cuu tre, cua triet
y nang » ky nang, ly nang, v nang
cam tu » cam thu, nam tu, dam tu
di cua » dai cua, doi cua, de cua
x hoi » xa hoi, o hoi, x ho

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 y nang x hoi. ((hieu va) or (hieu qua)) cam tu ((ban hanh) OR (ban hang)) di cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach y nang x hoi. ((hieu va) OR (hieu qua)) cam tu ((ban hanh) OR (ban hang)) di cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach y nang x hoi. ((hieu va) or (hieu qua)) cam tu ((ban hanh) OR (ban hang)) di cua tre".
• Adding a wildcard symbol may retrieve word variants: so sach y nang x hoi. ((hieu va) or (hieu qua)) cam tu ((ban hanh) OR (ban hang)) di cua tre*.