Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
hang dai » hoang dai, hang tai, hang dau
va hang » van hang, va nang, va lang
cao suc » cao duc
hieu ve » hieu va, hieu van
te sach » toc sach
cua tre » cua te, cuu tre, cua triet
nang o » nang co, nang ho, nang ro
o hai » co hai, so hai, o lai

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: ((thu sach) OR (te sach)) ky nang o hai. hieu ve ((cao suc) OR (cao su)) va hang dai cua tre~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((thu sach) or (te sach)) ky nang o hai. hieu ve ((cao suc) OR (cao su)) va hang dai cua tre~".
• Adding a wildcard symbol may retrieve word variants: ((thu sach) or (te sach)) ky nang o hai. hieu ve ((cao suc) OR (cao su)) va hang dai cua tre*.