Perhaps you should try some spelling variations:
dieu cua » dieu tra
va dang » van dang, va nang, va lang
cac tuc » cac toc, cac tac, cac nuoc
hieu ve » hieu va, hieu van
cao hoi » cau hoi, co hoi, cao hoc
sach va » sach xa, sach ha, sach dao
sach v » sach y, sach 2, sach vay
cac tu » cac thu, cach tu, cac du
cua te » cua tu

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

• Performing a fuzzy search may retrieve terms with similar spellings: su ((sach v) or (sach va)) nang cao hoi. hieu ve ((cac tuc) OR (cac tu)) va dang dieu cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sach v) OR (sach va)) nang cao hoi. hieu ve ((cac tuc) OR (cac tu)) va dang dieu cua te.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su ((sach v) or (sach va)) nang cao hoi. hieu ve ((cac tuc) OR (cac tu)) va dang dieu cua te".
• Adding a wildcard symbol may retrieve word variants: su ((sach v) or (sach va)) nang cao hoi. hieu ve ((cac tuc) OR (cac tu)) va dang dieu cua te*.