Perhaps you should try some spelling variations:
luong quan » thong quan, duong qua
dung quan » dung quang, dung luan, dang quang
hieu soat » hieu suat, hieu hoat, hieu luat
quang tan » quang tuan, quang tran, quang toan
kiem soat » kiem toan
van kiem » va kiem, van kien, van hieu
vi hieu » vi dieu, va hieu, vo hieu
tan van » tran van, tang van, luan 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) OR (luong quan)) vi hieu soat ) OR ( tinh quang tan van kiem 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 tan van kiem soat ))~".
• Adding a wildcard symbol may retrieve word variants: (( tinh ((dung quan) OR (luong quan)) vi hieu soat ) or ( tinh quang tan van kiem soat ))*.