Perhaps you should try some spelling variations:
thuoc sach » hoc sach, nuoc sach, thuat sach
toc sach » hoc sach, doc sach, nuoc sach
van hanh » van thanh, ban hanh, van anh
chu bang » thu bang, chuc nang, chu quang
hanh lai » hanh lam, hanh tai, thanh lap
cua tre » cua te, cua triet, dua tren
cac duc » cac du, cao duc, cac dac
duc van » duc va, duc tan, duc manh
hieu va » lieu va, hieu qua
bang xa » lang xa, bang va, mang xa
cuu tre » cau tren, cau treo

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