Perhaps you should try some spelling variations:
doc sach » hoc sach, toc sach, nuoc sach
hang vai » hang va, hang tai, hang hai
tay lang » tai lang, tay tang, tay quang
ban hang » ngan hang
quoc ban » quoc bao, quoc lan, quoc quan
cam quoc » cac quoc, cao quoc, nam quoc
vai cua » dai cua, hai cua, lai cua
cua tre » cua te, cuu tre, cua triet
hieu ve » hieu va, hieu van
van hoi » van hoa, van hoc, van hoe
y lang » o lang, _ lang, yen lang

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 ((y lang) or (tay lang)) van hoi. ((hieu ve) or (hieu qua)) cam quoc ban hang vai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc sach ((y lang) OR (tay lang)) van hoi. ((hieu ve) OR (hieu qua)) cam quoc ban hang vai cua tre.
• Adding a wildcard symbol may retrieve word variants: doc sach ((y lang) or (tay lang)) van hoi. ((hieu ve) or (hieu qua)) cam quoc ban hang vai cua tre*.