Perhaps you should try some spelling variations:
tinh dung » trinh dung, tin dung, tinh quang
hieu luat » hieu qua
hieu suat » hieu qua
quan dang » quang dang, quan lang, quan dong
dung lan » dung luan, dung land, dung lam
tinh qua » tinh quan, trinh qua, tinh cua
dieu hat » dieu hanh, dieu khac, dieu can
lan van » luan van, lang van, tan van

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( tinh dung lan van ((hieu luat) or (hieu suat)) ) or ( tinh qua quan dang dieu hat ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tinh dung lan van ((hieu luat) OR (hieu suat)) ) OR ( tinh qua quan dang dieu hat )).
• Adding a wildcard symbol may retrieve word variants: (( tinh dung lan van ((hieu luat) or (hieu suat)) ) or ( tinh qua quan dang dieu hat ))*.