Perhaps you should try some spelling variations:
dung ltan » dung luan, dung tai, dung nhan
hieu suat » hieu luat
tinh quan » tinh quang, trinh quan, tin quan
hien soat » thien hoat, kiem soat, bien soan
ltan van » luan van, tan van, tran van
quan lan » quan luan, quan lang, quan van
van hien » van hieu, van tien
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: (( trinh dung ltan van ((hieu suat) or (hieu qua)) ) or ( tinh quan lan van hien soat ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( trinh dung ltan van ((hieu suat) OR (hieu qua)) ) OR ( tinh quan lan van hien soat )).
• Adding a wildcard symbol may retrieve word variants: (( trinh dung ltan van ((hieu suat) or (hieu qua)) ) or ( tinh quan lan van hien soat ))*.