Perhaps you should try some spelling variations:
quang tran » quang tuan, quang trung, quang thanh
luong quan » thong quan, duong qua
dung quan » dung quang, dung luan, dang quang
hieu soat » hieu suat, hieu hoat, hieu luat
kien soat » kiem soat, bien soan, kien hoa
tran van » luan van
van kien » van tien, van hien, van chien
va hieu » van hieu, va dieu, va hien

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) OR (luong quan)) va hieu soat ) OR ( tinh quang tran van kien soat ))~.
• Adding a wildcard symbol may retrieve word variants: (( tinh ((dung quan) or (luong quan)) va hieu soat ) or ( tinh quang tran van kien soat ))*.