Perhaps you should try some spelling variations:
quang dung » quang trung, ung dung, cuong dung
thien hoat » trien hoat, thien thuat, tien hoa
tinh dung » trinh dung, tin dung, tinh huong
hieu soat » hieu suat, hieu hoat, hieu luat
hien hoat » dien hoat, hieu hoat, trien hoat
van hieu » cao hieu
dung van » duong van, dung va, dang van
luan » quan, lan

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