Perhaps you should try some spelling variations:
tinh dung » trinh dung, tin dung, tinh quang
hieu hoat » hieu hoa, thien hoat, hieu luat
hieu suat » hieu luat, hieu qua
trinh qua » trinh quan, trinh cua, trinh quang
quan dang » quang dang, quan lang, quan dong
dung lan » dung luan, dung land, dung lam
dieu can » dieu hanh, tiep can, dieu cua
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 hoat) or (hieu suat)) ) or ( trinh qua quan dang dieu can ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tinh dung lan van ((hieu hoat) OR (hieu suat)) ) OR ( trinh qua quan dang dieu can )).
• Adding a wildcard symbol may retrieve word variants: (( tinh dung lan van ((hieu hoat) or (hieu suat)) ) or ( trinh qua quan dang dieu can ))*.