Perhaps you should try some spelling variations:
duong luan » dung luan, dong luan, duong quan
hieu soat » hieu suat, hieu hoat, hieu luat
hien soat » thien hoat, kiem soat, bien soan
quan van » quan luan, quan doan, quang ban
van hien » van hieu, van tien
quan va » quan vi, quan ha, luan va
tinh » trinh, minh, kinh

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

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