Zotero 4.0 is a web-based, open-source citation management tool that is designed to store, manage, and cite bibliographic references, such as books and articles. In Zotero, each of these references constitutes an item. Items can be everything from books, articles, and documents to web pages, artwork, films, sound recordings, bills, cases, or statutes, among many others. Zotero is both a desktop application and a bowser extension with plug-ins to word processing programs.

Zotero is available with basic features for free, with a fee structure for additional storage.  Two options are available:

• Zotero for Firefox, a Firefox browser extension.
• Zotero Standalone is a desktop application that integrates with Google Chrome, Apple Safari and Firefox but without the integrated features of Zotero for Firefox. 

Documentation and tutorials:

• Zotero documentation
• Zotero screencasts
• Zotero tutorial from the Green Library at Stanford
• Information guide on Zotero from Georgia State University
• Information guide on Zotero from MIT

Third-Party add-ons:

CitationStyles.org is the home of the Citation Style Language (CSL), an open XML-based language to describe the formatting of citations and bibliographies.  CSL is used by Zotero, Mendeley and Papers to add and edit citation styles.

Paper Machines is an open-source extension for the Zotero bibliographic management software. Its purpose is to allow individual researchers to generate analyses and visualizations of user-provided text, without requiring extensive computational resources or technical knowledge.