Perhaps you should try some spelling variations:
quang quan » quang tuan, quang uan, quan quan
dung quang » dang quang, luong quang, dung luan
dung quan » dung luan, luong quan, dang quang
hieu soat » hieu suat, hieu hoat, hieu luat
kiem soat » kiem toan
van hieu » cao hieu
quan va » quan vi, quan ha, luan va
va kiem » van kien

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 quan) or (dung quang)) van hieu soat ) or ( tinh quang quan va kiem soat ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tinh ((dung quan) OR (dung quang)) van hieu soat ) OR ( tinh quang quan va kiem soat )).
• Adding a wildcard symbol may retrieve word variants: (( tinh ((dung quan) or (dung quang)) van hieu soat ) or ( tinh quang quan va kiem soat ))*.