I downloaded and tried:
Papers 3
End note X7
Bookends
Sente 7
In none of them I could easily change the citation system.
they all use american journals and so on.
In Italy, everything has a different style.
Is there a way to custom the citation system and abbreviations?
tks! 
In Papers3 you can specify in detail how references should look in the reference list, in Preferences if I remember correctly. If none of the built in alternatives look the way you want you just create your own style.
mekentosj.tenderapp.com/kb/getti … -citations
You can do the same in Bookends, but you’ll have to play around, as I don’t know the details. But customisation is built in.
i serached, but i found the customization tool just in bookends (very difficult to play with), not in papers
second question: would be possible to tell to the app to write the first time it encounters the citation in a way, and the second (third, etc) time in a different way?
first time: J. Ive, Play with iPhone, Apple, 2014, 1-5
other times: J. Ive, 4 OR J. Ive, Play, 4
Have a look a the CSL-styles pages; all these would be usable via Papers. As you can see there are 7000+ styles that can be used by several programs that have implemented the CSL-styles protocol. (I’m a http://www.zotero.org"> user; it works well with Scrivener – albeit not as smooth as I’d like it to – and involves a Firefox plugin for rtf/odf-scan.
very complicated… 
anyway, all the styles are for american and for medical journals…
nothing for law in different countries…
still searching and still haven’t found the way to modify styles…
too much complicated
The customisation tool in Bookends is very flexible – which is, of course, why it seems complicated! If it were simple, it wouldn’t offer the range of variation that it does. But if you go to Biblio > Formats Manager… and step through the supplied formats until you come across one that is similar to what you are looking for (according to the sample display at the bottom of the Bibliography Options and Citation Options tabs), then you can use that one as the basis for a new format of your own. Select it in the left-hand pane, then click on the “+” button to add a new format, and make your required changes in the tabs on the right. Bookends does allow you to present the first and subsequent instances of a citation in different ways (via the “First” and “Subsequent” fields in the Citation Options tab).
I once had to set up a really awkward citation style in Bookends to meet the requirements of a university course that I was doing, and in the end I had to resort to emailing Sonny Software for technical support. Although he clearly didn’t believe that anyone would want to present information in the way that I had been told to do, Jon was a great help in sorting it out. So if you are having trouble setting up your citation format in any of the applications that you are considering, don’t forget that you can ask the corresponding technical support team or user forum for assistance.
Siren,
tks for all, you have been very helpful! 
Abrazo,
Raf
I am a Papers3 user, and Papers3 seems to have made the same choice. In an earlier version one could design the reference list in any way one wanted, but now one is “restricted” to the CSL-styles available, so I was a bit to fast in saying it could be done manually. Obviously no more so.
BUT, I think that if someone had a list of reference styles, used in major international journals but not on the CSL-list, one could just contact Papers3 support and ask them to include this. On the Papers3 forum there has recently been an extensive discussion on how to use Apple script to get Papers3 to do all sorts of things, and a guy from the support team has provided scripts for users that asked for something special. So my advice would be: ask them! The Mekentosj team is pretty good at fixing things.
I’m a bit late to the discussion, but will chip in to say that EndNote also has thousands of formats built-in and also has the ability to customise any of them or make your own.
Having said that, if Papers meets your needs, I’d go with it - it is, in my opinion, the most user friendly of the citation apps (although still not as powerful or flexible as EndNote).
That stuff is all customizable in Endnote, too. You can add/customize the basic Reference Types, and you can easily duplicate and customize in-text and bibliographic citation styles for those reference types.
It is also likely that someone has already set up Endnote style files for the citation styles you seek. The Endnote people themselves have a big bank of them online that you can look through for what you need.
I am an Endnote user since Version 1.0.
–Greg