Perhaps you should try some spelling variations:
quang doan » quan doan, quang hoan, quang toan
hieu suat » hieu luat, hieu qua
dung land » dung luan, dung lam, dung san
tren hoat » trien hoat, trong hoat, thien hoat
dung lan » dung luan, dung lam, dung san
van hieu » cao hieu
doan van » doan va, hoang van, luan van
van tren » van tien, quan tren, van trung

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 lan) or (dung land)) van hieu suat ) or ( tinh quang doan van tren hoat ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( trinh ((dung lan) OR (dung land)) van hieu suat ) OR ( tinh quang doan van tren hoat )).
• Adding a wildcard symbol may retrieve word variants: (( trinh ((dung lan) or (dung land)) van hieu suat ) or ( tinh quang doan van tren hoat ))*.