Perhaps you should try some spelling variations:
tinh quan » tinh quang, trinh quan, tin quan
quan quan » quan quang, qua quan, quan luan
hieu suat » hieu luat, hieu qua
hien soat » thien hoat, kiem soat, bien soan
binh dan » minh danh, binh dinh, binh luan
dan dung » van dung, tin dung, ap dung
dung van » duong van, dung va, dang van
van hien » van hieu, van tien
quan vo » quan vi, quan va, quan ve
vo hieu » co hieu, va hieu, cao hieu

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: (( tinh quan quan vo hieu suat ) or ( binh dan dung van hien soat ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tinh quan quan vo hieu suat ) OR ( binh dan dung van hien soat )).
• Adding a wildcard symbol may retrieve word variants: (( tinh quan quan vo hieu suat ) or ( binh dan dung van hien soat ))*.