Perhaps you should try some spelling variations:
sach thue » sach thieu, sach tham, cach thuc
hieu van » hieu va, thien van, lieu va
hanh vai » hanh vi, hanh va, hanh tai
sach thu » sach thieu, sach tham, cach thuc
vai cua » dai cua, hai cua, lai cua
va hanh » van hanh, va thanh, va danh
chat do » chat deo, chat doc, chat co
cua tre » cua te, cuu tre, cua triet
hieu ve » hieu va
cao hoi » cau hoi, co hoi, cao hoc
do va » do van, so va

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

• Performing a fuzzy search may retrieve terms with similar spellings: thu ((sach thu) or (sach thue)) nang cao hoi. ((hieu ve) OR (hieu van)) chat do va hanh vai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu ((sach thu) OR (sach thue)) nang cao hoi. ((hieu ve) OR (hieu van)) chat do va hanh vai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu ((sach thu) or (sach thue)) nang cao hoi. ((hieu ve) OR (hieu van)) chat do va hanh vai cua tre".
• Adding a wildcard symbol may retrieve word variants: thu ((sach thu) or (sach thue)) nang cao hoi. ((hieu ve) OR (hieu van)) chat do va hanh vai cua tre*.