Perhaps you should try some spelling variations:
khong tang » khong cang, khong thanh, khong trong
hieu lang » chieu sang, hieu quang, nhieu tang
doanh cua » doanh luan
tang luan » dung luan
manh cua » ban cua
toan cau » toan cao, toan ban, toan tai
toan tap » toan ban
ho hieu » ho chieu, hoi hieu, nho hieu

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: ho hieu lang - canh ((manh cua) OR (doanh cua)) khong tang luan ((toan cau) OR (toan tap))~.
• Adding a wildcard symbol may retrieve word variants: ho hieu lang - canh ((manh cua) or (doanh cua)) khong tang luan ((toan cau) or (toan tap))*.