Global Warming. (2013). The History Channel website. Retrieved 7:55, May 23, 2013, from http://www.history.com/videos/global-warming.
Global Warming. [Internet]. 2013. The History Channel website. Available from: http://www.history.com/videos/global-warming [Accessed 23 May 2013].
“Global Warming.” 2013. The History Channel website. May 23 2013, 7:55 http://www.history.com/videos/global-warming.
“Global Warming,” The History Channel website, 2013, http://www.history.com/videos/global-warming [accessed May 23, 2013].
“Global Warming,” The History Channel website, http://www.history.com/videos/global-warming (accessed May 23, 2013).
Global Warming [Internet]. The History Channel website; 2013 [cited 2013 May 23] Available from: http://www.history.com/videos/global-warming.
Global Warming, http://www.history.com/videos/global-warming (last visited May 23, 2013).
Global Warming. The History Channel website. 2013. Available at: http://www.history.com/videos/global-warming. Accessed May 23, 2013.