Perhaps you should try some spelling variations:
quang quan » quang tuan, quang uan, quan quan
tinh huong » dinh huong, anh huong
tuan soat » quan sat, toan hoat, tuan hoan
hieu suat » hieu luat, hieu qua
quan van » luan van, quan luan, quan doan
van tuan » van quan, van ban, anh tuan
quan va » quan vi, quan ha, luan va
va hieu » van hieu, va dieu, va hien

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

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