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 » tan van, lan van, tran van
van hien » van hieu, van tien
luan » lan

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