Perhaps you should try some spelling variations:
hieu cua » hieu qua, dieu cua, bieu cua
lang van » dang van, tang van, hoang van
vai cua » dai cua, hai cua, lai cua
dao vai » dao van, dao va, dao bai
cac tuc » cac toc, cac tac, cac nuoc
tu sach » thu sach, su sach, te sach
lang xa » lang ha, dang xay
cua tre » cua te, cuu tre, cua triet
cac tu » cac thu, cach tu, cac du
va dao » ca dao

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach y ((lang xa) or (lang van)) hoi. hieu cua ((cac tuc) OR (cac tu)) va dao vai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach y ((lang xa) OR (lang van)) hoi. hieu cua ((cac tuc) OR (cac tu)) va dao vai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach y ((lang xa) or (lang van)) hoi. hieu cua ((cac tuc) OR (cac tu)) va dao vai cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach y ((lang xa) or (lang van)) hoi. hieu cua ((cac tuc) OR (cac tu)) va dao vai cua tre*.