Mountain Building. (2013). The History Channel website. Retrieved 6:07, May 21, 2013, from http://www.history.com/shows/how-the-earth-was-made/videos/playlists/web-exclusives.
Mountain Building. [Internet]. 2013. The History Channel website. Available from: http://www.history.com/shows/how-the-earth-was-made/videos/playlists/web-exclusives [Accessed 21 May 2013].
“Mountain Building.” 2013. The History Channel website. May 21 2013, 6:07 http://www.history.com/shows/how-the-earth-was-made/videos/playlists/web-exclusives.
“Mountain Building,” The History Channel website, 2013, http://www.history.com/shows/how-the-earth-was-made/videos/playlists/web-exclusives [accessed May 21, 2013].
“Mountain Building,” The History Channel website, http://www.history.com/shows/how-the-earth-was-made/videos/playlists/web-exclusives (accessed May 21, 2013).
Mountain Building [Internet]. The History Channel website; 2013 [cited 2013 May 21] Available from: http://www.history.com/shows/how-the-earth-was-made/videos/playlists/web-exclusives.
Mountain Building, http://www.history.com/shows/how-the-earth-was-made/videos/playlists/web-exclusives (last visited May 21, 2013).
Mountain Building. The History Channel website. 2013. Available at: http://www.history.com/shows/how-the-earth-was-made/videos/playlists/web-exclusives. Accessed May 21, 2013.