Perhaps you should try some spelling variations:
doc sach » hoc sach, toc sach, nuoc sach
thu mang » thu hang, thu bang, thu dang
ban hanh » ban hang
van hanh » van thanh, van anh, van ban
sach thu » sach thue, sach thieu, sach tham
tai cua » thai cua, tai cuc, tri cua
cua tre » cua te, cuu tre, cua triet
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

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) OR (ban hanh)) tai cua 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) OR (ban hanh)) tai cua 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) OR (ban hanh)) tai cua tre".
• Adding a wildcard symbol may retrieve word variants: doc sach thu mang xa hoi. hieu va ((cac duc) or (cac dac)) ((van hanh) OR (ban hanh)) tai cua tre*.