Perhaps you should try some spelling variations:
dung ltan » dung luan, dung tai, dung nhan
hieu suat » hieu luat, hieu qua
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 hieu » cao hieu
van hien » 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 ( 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 ( tinh quan luan van hien soat )).
• Adding a wildcard symbol may retrieve word variants: (( trinh dung ltan van hieu suat ) or ( tinh quan luan van hien soat ))*.