Perhaps you should try some spelling variations:
thuoc sach » hoc sach, nuoc sach, thuat sach
toc sach » hoc sach, doc sach, nuoc sach
hanh lai » hanh lam, hanh tai, thanh lap
van hanh » van thanh, ban hanh, van anh
lai cua » dai cua, hai cua, lai chau
duc van » duc va, duc tan, duc manh
cac duc » cac du, cao duc, cac dac
cua tre » cua te, cuu tre, cua triet
hieu va » lieu va
thu ban » thu hang
ban xa » ban va, ban ma, ban da

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