Perhaps you should try some spelling variations:
trinh chuan » trinh han, trinh quan, trinh luan
chuan luan » chuyen luan, chuan doan, quan luan
hieu suat » hieu luat, hieu qua
dung nang » dung dang, dung quang, dung thang
kien soat » kiem soat, bien soan, kien hoa
dun nang » den nang, luan nang, xuan nang
van hieu » cao hieu
van kien » van tien, van hien, van chien

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 nang) OR (dun nang)) van hieu suat ) OR ( trinh chuan luan van kien soat ))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( trinh ((dung nang) OR (dun nang)) van hieu suat ) or ( trinh chuan luan van kien soat ))~".
• Adding a wildcard symbol may retrieve word variants: (( trinh ((dung nang) OR (dun nang)) van hieu suat ) or ( trinh chuan luan van kien soat ))*.