A citation is essentially a reference to a source of information -- a book, an article, a webpage, or any other resource, physical or virtual. As such, it is a kind of avatar -- a summary, descriptive stand-in for the object itself.
The purpose of a citation or reference is two-fold. In the first instance, it is an attribution or recognition of the contributions of another researcher, commentator, or author to the work at hand. In the second instance, it is a pathway or, perhaps, a signpost leading others to that contributory source.
Zotero
(pronounced "zoh-TAIR-oh") is a free and open source citation management tool that collects, manages, and cites research sources by analysing the content in your web browser, and saving it to your personal library with a single click. It's easy to use, works on almost any website, and best of all it's free! It allows you to:
Zotero Standalone and Zotero Connector (for Chrome, Firefox, Safari, Opera)
Zotero Standalone is a separate, browser-independent application. Because Zotero Standalone lives outside your browser, it lacks some advanced features. To realize the full capability of Zotero Standalone, you must also install a Zotero Connector, available for Chrome, Safari, and Opera.
Citation Styles
Zotero comes with several popular citation styles for creating citations and bibliographies, and over 9,000 additional styles can be added by clicking "Edit" and "Preferences". Then, under the "Cite" tab, you can select "Get additional styles...".
Then you can select from over 9,000 styles or search for a specific style.