Perhaps you should try some spelling variations:
dung quang » dang quang, dung quan, luong quang
dung qsan » dung quan, dung san, dung luan
hieu suat » hieu luat, hieu qua
quang tan » quang tuan, quang tran, quang toan
kiem soat » kiem toan
van hieu » cao hieu
van kiem » va kiem, van kien, van hien
tan van » tran van, tang van, luan van

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( tinh ((dung qsan) or (dung quang)) van hieu suat ) or ( tinh quang tan van kiem soat ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tinh ((dung qsan) OR (dung quang)) van hieu suat ) OR ( tinh quang tan van kiem soat )).
• Adding a wildcard symbol may retrieve word variants: (( tinh ((dung qsan) or (dung quang)) van hieu suat ) or ( tinh quang tan van kiem soat ))*.