Perhaps you should try some spelling variations:
quang trong » quang truong, quang trung, quan trong
dung ltrong » dung trong, dung trung, dung luong
ltrong van » trong va, thong van, truong van
hieu suat » hieu luat, hieu qua
trong van » trong cac
bien soan » bien so
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 ltrong van hieu suat ) or ( tinh quang trong van bien soan ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tin dung ltrong van hieu suat ) OR ( tinh quang trong van bien soan )).
• Adding a wildcard symbol may retrieve word variants: (( tin dung ltrong van hieu suat ) or ( tinh quang trong van bien soan ))*.