Perhaps you should try some spelling variations:
trinh quan » tinh quang, trinh han
nhung cong » dung cong, thong cong, hang cong
hieu lang » chieu sang, hieu quang, nhieu tang
hai hieu » hai chieu, hoi hieu, phan hieu
cong tap » cuong tap, cong tac, cong tan
tap toan » tap doan, tap quan, bai toan
toan ban » van ban

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: hai hieu lang - hanh ((trinh quan) OR (trinh luat)) nhung cong tap toan ban~.
• Adding a wildcard symbol may retrieve word variants: hai hieu lang - hanh ((trinh quan) or (trinh luat)) nhung cong tap toan ban*.