Perhaps you should try some spelling variations:
doc sach » hoc sach, toc sach, nuoc sach
sach thu » sach thue, sach thieu, sach tham
thu mang » thu hang, thu bang, thu dang
hanh tai » thanh tai, hang tai, han tai
van hanh » van thanh, ban hanh, van anh
cua tre » cua te, cua triet, dua tren
cac dac » cac dan, cac dai, cac bac
cac duc » cac du, cao duc, cac nuoc
hieu va » lieu va, hieu qua
mang xa » lang xa, mang may, dang xay
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: doc sach thu mang xa hoi. hieu va ((cac duc) or (cac dac)) van hanh tai ((cua tre) OR (cuu tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc sach thu mang xa hoi. hieu va ((cac duc) OR (cac dac)) van hanh tai ((cua tre) OR (cuu tre)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc sach thu mang xa hoi. hieu va ((cac duc) or (cac dac)) van hanh tai ((cua tre) OR (cuu tre))".
• Adding a wildcard symbol may retrieve word variants: doc sach thu mang xa hoi. hieu va ((cac duc) or (cac dac)) van hanh tai ((cua tre) OR (cuu tre))*.