Perhaps you should try some spelling variations:
tinh dung » trinh dung, tin dung, tinh quang
hieu soat » hieu suat, hieu hoat, hieu luat
dung quan » dung quang, dung luan, luong quan
quan doan » quan hoang, chuan doan, chan doan
doan bien » doan dien, doan thien, doanh tien
bien soan » bien so
van hieu » cao hieu

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( tinh dung (luan OR lan) van hieu soat ) or ( tinh dung quan doan bien soan ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tinh dung (luan OR lan) van hieu soat ) OR ( tinh dung quan doan bien soan )).
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( tinh dung (luan OR lan) van hieu soat ) or ( tinh dung quan doan bien soan ))".
• Adding a wildcard symbol may retrieve word variants: (( tinh dung (luan OR lan) van hieu soat ) or ( tinh dung quan doan bien soan ))*.