Perhaps you should try some spelling variations:
trien hoat » tien hoa
hieu suat » hieu luat, hieu qua
duong tan » duong tuan, duong van, duong tai
tinh dung » trinh dung, tin dung, tinh quang
van trien » van tien, va trien, van tren
dung tan » dung toan, dung tai, dung san
van hieu » cao hieu

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

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