Perhaps you should try some spelling variations:
quang trong » quang truong, quang trung, quan trong
sang quang » dang quang, hang quang, tang quang
tinh sang » tinh quang, tinh trang, trinh san
trong thi » trong thoi, trong thu, trong tho
tinh chan » tinh chat, tinh than, tinh can
hieu suat » hieu luat, hieu qua
doan van » doan va, hoang van, luan van
van hieu » cao hieu
thi van » thi lan, thi hanh, thi nang

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( tinh sang quang trong thi van ) or ( tinh chan doan van hieu suat ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tinh sang quang trong thi van ) OR ( tinh chan doan van hieu suat ))*.