Perhaps you should try some spelling variations:
luong quan » thong quan, duong qua
tinh dung » trinh dung, tin dung, tinh quang
dung quan » dung quang, dang quang, dung cua
hieu soat » hieu suat, hieu hoat, hieu luat
bien soan » bien so
van bien » van tien, van hien, vat bien
luan » lan

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

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