Perhaps you should try some spelling variations:
dung quang » dang quang, luong quang, dung ung
tinh dung » trinh dung, tin dung, tinh quang
hieu suat » hieu luat, hieu qua
dung quan » luong quan, dang quang, dung cua
kiem soat » kiem toan
quan van » luan van, quan va, quan luan
van kiem » va kiem, van kien, van hieu
cu hieu » cua hieu, cuu hieu, co 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: (( tinh ((dung quang) OR (dung luan)) cu hieu suat ) OR ( tinh dung quan van kiem soat ))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( tinh ((dung quang) OR (dung luan)) cu hieu suat ) or ( tinh dung quan van kiem soat ))~".
• Adding a wildcard symbol may retrieve word variants: (( tinh ((dung quang) OR (dung luan)) cu hieu suat ) or ( tinh dung quan van kiem soat ))*.