Perhaps you should try some spelling variations:
dung quan » dung quang, dung luan, luong quan
hieu soat » hieu suat, hieu hoat, hieu luat
quang tan » quang tuan, quang tran, quang toan
kien soat » kiem soat, kien hoa, dien hoat
bien soan » bien so
quan cao » quang cao, quan cau, quan ao
tan van » tran van, tang van, luan van

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