World Trade Center. (2013). The History Channel website. Retrieved 1:51, May 23, 2013, from http://www.history.com/topics/world-trade-center.
World Trade Center. [Internet]. 2013. The History Channel website. Available from: http://www.history.com/topics/world-trade-center [Accessed 23 May 2013].
“World Trade Center.” 2013. The History Channel website. May 23 2013, 1:51 http://www.history.com/topics/world-trade-center.
“World Trade Center,” The History Channel website, 2013, http://www.history.com/topics/world-trade-center [accessed May 23, 2013].
“World Trade Center,” The History Channel website, http://www.history.com/topics/world-trade-center (accessed May 23, 2013).
World Trade Center [Internet]. The History Channel website; 2013 [cited 2013 May 23] Available from: http://www.history.com/topics/world-trade-center.
World Trade Center, http://www.history.com/topics/world-trade-center (last visited May 23, 2013).
World Trade Center. The History Channel website. 2013. Available at: http://www.history.com/topics/world-trade-center. Accessed May 23, 2013.