Perhaps you should try some spelling variations:
hieu soat » hieu hoat, hieu luat, kiem soat
hieu suat » hieu luat, hieu qua
tinh quan » tinh quang, trinh quan, tin quan
quan quan » quan quang, qua quan, quan luan
tien hoa » dien hoa, trien hoat, tien va
he tien » le tien, he lien, he mien
luan » lan

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