What are some alternatives?
Mendeley - Easily organize your papers, read & annotate your PDFs, collaborate in private or open groups, and securely access your research from everywhere.
Docear - Docear
JabRef - Graphical Java application for managing bibtex (. bib) databases.JabRef · JabRef Help · JabRef | Blog · OpenOffice/LibreOffice .
EndNote - EndNote is the industry standard when it comes to reference management in a comprehensive format.
Paperpile - Clean and simple and reference management for the web. Sync your PDFs to Google Drive and cite your papers in Google Docs.
Weava - Workspace to highlight, organize & collaborate on your research articles.