Perhaps you should try some spelling variations:
tinh dung » trinh dung, tin dung, tinh huong
dung quan » dung quang, dung luan, luong quan
hieu suat » hieu qua
hieu luat » hieu qua
quang uan » quang tuan, quang ban, quang tran
kien soat » kiem soat, bien soan, kien hoa
quan van » luan van, quan va, quan luan
van kien » van tien, van hien, van chien
uan van » luan van, tan van, san van

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 van ((hieu suat) OR (hieu luat)) ) OR ( tinh quang uan van kien soat ))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( tinh dung quan van ((hieu suat) OR (hieu luat)) ) or ( tinh quang uan van kien soat ))~".
• Adding a wildcard symbol may retrieve word variants: (( tinh dung quan van ((hieu suat) OR (hieu luat)) ) or ( tinh quang uan van kien soat ))*.