Perhaps you should try some spelling variations:
ban thanh » ban hanh
tac quang » thac quang, tac quan, tai quang
ban hang » ngan hang
sach tac » sach bac, sach tai, sach tham
nhan luc » nang luc
so sach » so sanh, bo sach, co sach
tai cua » thai cua, tai cuc, tri cua
va nhan » van nhan, ca nhan, va phan
hieu va » lieu va, hieu qua
cua tre » cua te, cuu tre, cua triet
va hoa » va hoc, 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 tac quang ((va hoa) or (van hoa)). hieu va nhan luc ((ban thanh) or (ban hang)) tai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach tac quang ((va hoa) OR (van hoa)). hieu va nhan luc ((ban thanh) OR (ban hang)) tai cua tre.
• Adding a wildcard symbol may retrieve word variants: so sach tac quang ((va hoa) or (van hoa)). hieu va nhan luc ((ban thanh) or (ban hang)) tai cua tre*.