Hello Javier. I use Zotero, but I think Mendeley also uses CSL styles. What I normally do, is find a style very similar to which I need (eg, search one in https://www.zotero.org/styles) and then edit it. for the edition I use this editor (http://editor.citationstyles.org/visualEditor/). By using this editor, you can arrange each of the necessary changes or authors instructions. Any problem with the CSL, just let me know with a message. I answered this in english, because you made your question in english!! jeje. Nos vemos.