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

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 bang xa hoi. ((hieu va) OR (lieu va)) 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 bang xa hoi. ((hieu va) OR (lieu va)) 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 bang xa hoi. ((hieu va) OR (lieu va)) cac duc van hanh lai cua tre".
• Adding a wildcard symbol may retrieve word variants: ((toc sach) or (thuoc sach)) thu bang xa hoi. ((hieu va) OR (lieu va)) cac duc van hanh lai cua tre*.