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

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

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