Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hieu van » hieu va, thien van, lieu va
nam thuc » nam thuoc, am thuc, nam thu
thuc ban » thuoc ban, thuc dan, thu ban
ban hanh » ban hang
hanh doi » thanh doi, hanh noi, hang doi
doi cua » dai cua, hoi cua
cua tre » cua te, cuu tre, cua triet
o hoc » mo hoc, so hoc, y hoc

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: ((te sach) OR (toc sach)) ky nang ((o hoc) OR (co hoc)). hieu van nam thuc ban hanh doi cua tre~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((te sach) or (toc sach)) ky nang ((o hoc) OR (co hoc)). hieu van nam thuc ban hanh doi cua tre~".
• Adding a wildcard symbol may retrieve word variants: ((te sach) or (toc sach)) ky nang ((o hoc) OR (co hoc)). hieu van nam thuc ban hanh doi cua tre*.