Perhaps you should try some spelling variations:
tinh dung » trinh dung, tin dung, tinh quang
dung quan » dung quang, dung luan, luong quan
hieu hoat » thien hoat, hieu luat, hieu suat
tinh nang » trinh nang, tin nang, tich nang
nang quan » ban quan, nang suat
hien soat » thien hoat, kiem soat, bien soan
quan cao » quang cao, quan cau, quan ao
hieu hoa » tieu hoa, dieu hoa, hiep hoa
quan van » luan van, quan va, quan luan
van hien » van hieu, van tien

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 cao ((hieu hoat) OR (hieu hoa)) ) OR ( tinh nang quan van hien soat ))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( tinh dung quan cao ((hieu hoat) OR (hieu hoa)) ) or ( tinh nang quan van hien soat ))~".
• Adding a wildcard symbol may retrieve word variants: (( tinh dung quan cao ((hieu hoat) OR (hieu hoa)) ) or ( tinh nang quan van hien soat ))*.