Perhaps you should try some spelling variations:
hieu suat » hieu luat, hieu qua
hieu soat » hieu hoat, hieu luat, kiem soat
dien soan » bien soan, dien toan, dien hoa
dung lan » dung land, dung lam, dung san
lan van » luan van, lang van, tan van
luan va » luan van, luat va
va dien » va dieu, va lien, mai dien

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( trinh dung lan van ((hieu soat) OR (hieu suat)) ) or ( tin dung luan va dien soan ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( trinh dung lan van ((hieu soat) OR (hieu suat)) ) OR ( tin dung luan va dien soan )).
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( trinh dung lan van ((hieu soat) OR (hieu suat)) ) or ( tin dung luan va dien soan ))".
• Adding a wildcard symbol may retrieve word variants: (( trinh dung lan van ((hieu soat) OR (hieu suat)) ) or ( tin dung luan va dien soan ))*.