History of Pyramids. (2013). The History Channel website. Retrieved 1:03, May 21, 2013, from http://www.history.com/shows/mankind-the-story-of-all-of-us/interactives/history-of-pyramids.
History of Pyramids. [Internet]. 2013. The History Channel website. Available from: http://www.history.com/shows/mankind-the-story-of-all-of-us/interactives/history-of-pyramids [Accessed 21 May 2013].
“History of Pyramids.” 2013. The History Channel website. May 21 2013, 1:03 http://www.history.com/shows/mankind-the-story-of-all-of-us/interactives/history-of-pyramids.
“History of Pyramids,” The History Channel website, 2013, http://www.history.com/shows/mankind-the-story-of-all-of-us/interactives/history-of-pyramids [accessed May 21, 2013].
“History of Pyramids,” The History Channel website, http://www.history.com/shows/mankind-the-story-of-all-of-us/interactives/history-of-pyramids (accessed May 21, 2013).
History of Pyramids [Internet]. The History Channel website; 2013 [cited 2013 May 21] Available from: http://www.history.com/shows/mankind-the-story-of-all-of-us/interactives/history-of-pyramids.
History of Pyramids, http://www.history.com/shows/mankind-the-story-of-all-of-us/interactives/history-of-pyramids (last visited May 21, 2013).
History of Pyramids. The History Channel website. 2013. Available at: http://www.history.com/shows/mankind-the-story-of-all-of-us/interactives/history-of-pyramids. Accessed May 21, 2013.