Perhaps you should try some spelling variations:
dung quang » dang quang, dung quan, luong quang
hieu suat » hieu luat, hieu qua
quang van » quang ban, quan van, quang uan
bien soan » bien so
dung chi » dung cho, dung chien, chung chi
dung thi » dung tai, dung tri, dung thu
van hieu » cao hieu
van bien » van tien, van hien, vat bien

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 chi) or (dung thi)) van hieu suat ) or ( tin dung quang van bien soan ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tin ((dung chi) OR (dung thi)) van hieu suat ) OR ( tin dung quang van bien soan )).
• Adding a wildcard symbol may retrieve word variants: (( tin ((dung chi) or (dung thi)) van hieu suat ) or ( tin dung quang van bien soan ))*.