Perhaps you should try some spelling variations:
thien hoat » trien hoat, thien thuat, tien hoa
tinh dung » trinh dung, tin dung, tinh huong
hieu suat » hieu luat, hieu qua
quang uan » quang tuan, quang ban, quang tran
hien soat » kiem soat, bien soan, hien luat
dung lan » dung luan, dung land, dung lam
van hieu » cao hieu
lan van » luan van, lang van, tan van
uan van » luan van, quan van, tan 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 lan van hieu suat ) OR ( tinh quang uan van ((hien soat) OR (thien hoat)) ))~.
• Adding a wildcard symbol may retrieve word variants: (( tinh dung lan van hieu suat ) or ( tinh quang uan van ((hien soat) or (thien hoat)) ))*.