Perhaps you should try some spelling variations:
quang luan » quan luan, quang tuan, quang uan
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
van kien » van tien, van hien, van chien
vi hieu » vi dieu, va hieu, vo hieu

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