Perhaps you should try some spelling variations:
quang tran » quang tuan, quang trung, quang thanh
dung quan » dung quang, dung luan, luong quan
hieu soat » hieu suat, hieu hoat, hieu luat
quan van » luan van, quan va, quan luan
van hieu » cao hieu
van kien » van hien, van chien
van tien » toan tien, van tuan

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