Perhaps you should try some spelling variations:
tinh dung » trinh dung, tin dung, tinh quang
dung quan » dung quang, dung luan, luong quan
hieu suat » hieu luat, hieu qua
quang cua » quan cua, quang tuan, quang huy
hieu soat » hieu hoat, hieu luat, kiem soat
van hieu » cao hieu
quan ha » quan he
ha hieu » nha hieu, va hieu, phan hieu
luan » lan

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