Perhaps you should try some spelling variations:
hanh hoi » hanh thoi, hanh noi, hanh hoa
ban hanh » ban hang
sach thu » sach thue, sach tham, cach thuc
cac duc » cac du, cao duc, cac dac
hoi cua » hoi chuc
duc ban » duc tan, duc van, dua ban
hieu va » hieu qua
cua tre » cua te, cuu tre, cua triet
bang va » hang va, ban va, trang va
va hoi » xa hoi, va hoc, va hoa

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

• Performing a fuzzy search may retrieve terms with similar spellings: toc ((sach thu) or (sach thieu)) bang va hoi. ((hieu va) OR (lieu va)) cac duc ban hanh hoi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc ((sach thu) OR (sach thieu)) bang va hoi. ((hieu va) OR (lieu va)) cac duc ban hanh hoi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc ((sach thu) or (sach thieu)) bang va hoi. ((hieu va) OR (lieu va)) cac duc ban hanh hoi cua tre".
• Adding a wildcard symbol may retrieve word variants: toc ((sach thu) or (sach thieu)) bang va hoi. ((hieu va) OR (lieu va)) cac duc ban hanh hoi cua tre*.