[Jabref-users] Import not detecting duplicates

[Mélanie T. <me...@ya...>]

Hi,
I'm almost desesperate! ;-) I already posted on forum but I didn't get 
answer so I try here.
I want to merge some references  (in .bib file) created in other 
softwares (bibus and Mendeley). Both are :
author = {LastName, FirstName and LastName, FirstName},

But my main database (references were fetched in Pubmed in Jabref)
author = {FirstName LastName and FirstName LastName},

So when I add them, they are not detected as duplicates. Rest of 
reference, as almost I can see, is exactly the same.
So, my questions:
1- What is the rationale for duplicates? Author, title, journal??
2- How can I import and change the way authors are written?
3- Any other thoughts that could help to solve my problem...

Thanks
Mélanie