Perhaps you should try some spelling variations:
khung luan » chung luan, dung luan, hang luan
tinh khung » trinh khung, tinh hung, tinh khang
trinh han » trinh quan
han quang » phan quang, hang quang, than quang
quang van » quang ban, quan van, quang uan
hieu suat » hieu luat, hieu qua
tien soat » trien hoat, thien hoat, kiem soat
van hieu » cao hieu
van tien » toan tien, van tuan

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( trinh han quang van hieu suat ) or ( tinh khung luan van tien soat ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( trinh han quang van hieu suat ) OR ( tinh khung luan van tien soat ))*.