Perhaps you should try some spelling variations:
quang tang » quang thang, quang dang, quang tung
thien hoat » trien hoat, thien thuat, tien hoa
dung lang » dung dang, dung nang, dung land
hieu suat » hieu luat, hieu qua
hien soat » kiem soat, bien soan, hien luat
lang cao » nang cao, lang co, quang cao
tang van » dang van, hoang van, trong 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: (( trinh dung lang cao hieu suat ) OR ( tinh quang tang van ((hien soat) OR (thien hoat)) ))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( trinh dung lang cao hieu suat ) or ( tinh quang tang van ((hien soat) OR (thien hoat)) ))~".
• Adding a wildcard symbol may retrieve word variants: (( trinh dung lang cao hieu suat ) or ( tinh quang tang van ((hien soat) OR (thien hoat)) ))*.