Perhaps you should try some spelling variations:
tinh dung » trinh dung, tin dung, tinh quang
dung quan » dung quang, dung luan, luong quan
hieu soat » hieu suat, hieu hoat, hieu luat
luan bien » luan lien, xuan bien, luong bien
quan van » luan van, quan va, quan doan
van hieu » cao hieu
bien so » bien doi

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