Perhaps you should try some spelling variations:
sang quang » dang quang, tang quang, van quang
hang quang » dang quang, hong quang, hang quan
tinh dung » trinh dung, tin dung, tinh quang
hieu suat » hieu luat, hieu qua
van kien » van tien, van hien, van chien
kien hoa » dien hoa, tien hoa, kien ha
van hieu » cao hieu
luan » quan, lan

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: (( tinh ((sang quang) OR (hang quang)) van kien hoa ) OR ( tinh dung luan van hieu suat ))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( tinh ((sang quang) OR (hang quang)) van kien hoa ) or ( tinh dung luan van hieu suat ))~".
• Adding a wildcard symbol may retrieve word variants: (( tinh ((sang quang) OR (hang quang)) van kien hoa ) or ( tinh dung luan van hieu suat ))*.