Zotero (pronounced "zoh-TAIR-oh") is a browser add-on that collects, manages, and cites research sources. It's easy to use, lives in your web browser where you do your work, and best of all it's free. Zotero allows you to attach PDFs, notes and images to your citations, organize them into collections for different projects, and create bibliographies.
In need of citation help? Here are a few resources that may be helpful.
Purdue OWL - assists students with academic writing.
Excelsior Online Writing Lab-provides guidance with APA citations.