Freitas, N. (2015, January 6). People around the world are voluntarily submitting to China’s Great Firewall. Why? Retrieved from http://www.slate.com/blogs/future_tense/2015/01/06/
Nafees, Q., Yilong, Y., Andras, N., Zhiming, L., & Janos, S. (2014, November 19). Anonymously analyzing clinical data sets. Retrieved from http://arxiv.org/abs/1501.05916
Sea Turtle Restoration Project. (2006). Threats to sea turtles. Retrieved from http://www.seaturtleinc.org/rehabilitation/threats-to-sea-turtles/
Date retrieved: If you think that the content of a Web site will change over time, you can include the date that you viewed the cited information in your "retrieved from" line.
(Nafees, Yilong, Andras, Zhiming, & Janos, 2014)
(Sea Turtle Restoration Project, 2006)
If you refer to an entire Web site, you do not need to include an entry for it in your reference list, but must identify the source clearly in the text of your paper. For example:
The Sea Turtle Restoration Project homepage presents a wealth of compelling, well-researched information on the struggle to save the world's sea turtles from extinction (http://www.seaturtles.org).
See Style Guide, pp. 31-34.