Perhaps you should try some spelling variations:
quan quang » qua quang, quan quan, xuan quang
quat quang » luat quang, xuat quang, qua quang
tinh khong » tinh khang, tinh huong, benh khong
khong luan » thong luan, khong quan, khung luan
hieu soat » hieu suat, hieu hoat, hieu luat
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 ((quan quang) OR (quat quang)) van hieu soat ) or ( tinh khong luan van tien soat ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( trinh ((quan quang) OR (quat quang)) van hieu soat ) OR ( tinh khong luan van tien soat )).
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( trinh ((quan quang) OR (quat quang)) van hieu soat ) or ( tinh khong luan van tien soat ))".
• Adding a wildcard symbol may retrieve word variants: (( trinh ((quan quang) OR (quat quang)) van hieu soat ) or ( tinh khong luan van tien soat ))*.