Perhaps you should try some spelling variations:
dung quan » dung quang, dung luan, luong quan
hieu soat » hieu suat, hieu hoat, kiem soat
hieu luat » hieu qua
quang tan » quang tuan, quang tran, quang toan
kien soat » kiem soat, bien soan, kien hoa
van kien » van tien, van hien, van chien
quan va » quan vi, quan ha, luan va
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: (( trinh dung quan va ((hieu soat) or (hieu luat)) ) or ( tinh quang tan van kien soat ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( trinh dung quan va ((hieu soat) OR (hieu luat)) ) OR ( tinh quang tan van kien soat )).
• Adding a wildcard symbol may retrieve word variants: (( trinh dung quan va ((hieu soat) or (hieu luat)) ) or ( tinh quang tan van kien soat ))*.