Perhaps you should try some spelling variations:
cac trong » cay trong, tac trong, ca trong
sach thu » sach thue, sach thieu, sach tham
doi cua » dai cua, hoi cua
qua hai » qua hoat
hai tuc » thai tuc, hai cuc, thai thuc
sach ty » sach y, sach tu, xach tay
cua tre » cua te, cuu tre, cua triet
x hoi » xa hoi, o hoi, x ho

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

• Performing a fuzzy search may retrieve terms with similar spellings: co ((sach ty) or (sach thu)) nang x hoi. hieu qua hai tuc ((cac trong) OR (cac truong)) doi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: co ((sach ty) OR (sach thu)) nang x hoi. hieu qua hai tuc ((cac trong) OR (cac truong)) doi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "co ((sach ty) or (sach thu)) nang x hoi. hieu qua hai tuc ((cac trong) OR (cac truong)) doi cua tre".
• Adding a wildcard symbol may retrieve word variants: co ((sach ty) or (sach thu)) nang x hoi. hieu qua hai tuc ((cac trong) OR (cac truong)) doi cua tre*.