Zotero is a free, easy-to-use, tool helping you collect, organize, cite, and share your research sources.
The software is available for multiple operating systems: Mac, Windows, and Linux.
Zotero is one of the best free resources for online data collection and research, which automatically senses content in your web browser, allowing you to add it to your personal library with a single click.
Zotero collects all your research in a single, searchable interface. You can add PDFs, images, audio and video files, snapshots of web pages, and really anything else. Zotero automatically indexes the full-text content of your library, enabling you to find exactly what you're looking for with just a few keystrokes.
The free version provides free 100 MB free online storage.
With groups’ capability, you may share your work, or sources you have discovered, with others who are working in related areas. Collaborate with colleagues, publicly or privately, on ongoing research. Discover other people with similar interests and the sources they are citing.