Perhaps you should try some spelling variations:
quang uan » quang tuan, quang ban, quang tran
hieu suat » hieu luat, hieu qua
kien soat » kiem soat, bien soan, kien hoa
dung lan » dung luan, dung land, dung lam
van hieu » cao hieu
van kien » van tien, van hien, van chien
lan van » luan van, lang van, tan van
uan van » luan van, quan van, tan 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 lan van hieu suat ) or ( tinh quang uan van kien soat ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tin dung lan van hieu suat ) OR ( tinh quang uan van kien soat )).
• Adding a wildcard symbol may retrieve word variants: (( tin dung lan van hieu suat ) or ( tinh quang uan van kien soat ))*.