Radio Astronomy Points to Extraterrestrial Life. (2013). The History Channel website. Retrieved 12:14, May 25, 2013, from http://www.history.com/speeches/radio-astronomy-points-to-extraterrestrial-life.
Radio Astronomy Points to Extraterrestrial Life. [Internet]. 2013. The History Channel website. Available from: http://www.history.com/speeches/radio-astronomy-points-to-extraterrestrial-life [Accessed 25 May 2013].
“Radio Astronomy Points to Extraterrestrial Life.” 2013. The History Channel website. May 25 2013, 12:14 http://www.history.com/speeches/radio-astronomy-points-to-extraterrestrial-life.
“Radio Astronomy Points to Extraterrestrial Life,” The History Channel website, 2013, http://www.history.com/speeches/radio-astronomy-points-to-extraterrestrial-life [accessed May 25, 2013].
“Radio Astronomy Points to Extraterrestrial Life,” The History Channel website, http://www.history.com/speeches/radio-astronomy-points-to-extraterrestrial-life (accessed May 25, 2013).
Radio Astronomy Points to Extraterrestrial Life [Internet]. The History Channel website; 2013 [cited 2013 May 25] Available from: http://www.history.com/speeches/radio-astronomy-points-to-extraterrestrial-life.
Radio Astronomy Points to Extraterrestrial Life, http://www.history.com/speeches/radio-astronomy-points-to-extraterrestrial-life (last visited May 25, 2013).
Radio Astronomy Points to Extraterrestrial Life. The History Channel website. 2013. Available at: http://www.history.com/speeches/radio-astronomy-points-to-extraterrestrial-life. Accessed May 25, 2013.