Edison's first great invention. (2013). The History Channel website. Retrieved 2:07, May 20, 2013, from http://www.history.com/this-day-in-history/edisons-first-great-invention.
Edison's first great invention. [Internet]. 2013. The History Channel website. Available from: http://www.history.com/this-day-in-history/edisons-first-great-invention [Accessed 20 May 2013].
“Edison's first great invention.” 2013. The History Channel website. May 20 2013, 2:07 http://www.history.com/this-day-in-history/edisons-first-great-invention.
“Edison's first great invention,” The History Channel website, 2013, http://www.history.com/this-day-in-history/edisons-first-great-invention [accessed May 20, 2013].
“Edison's first great invention,” The History Channel website, http://www.history.com/this-day-in-history/edisons-first-great-invention (accessed May 20, 2013).
Edison's first great invention [Internet]. The History Channel website; 2013 [cited 2013 May 20] Available from: http://www.history.com/this-day-in-history/edisons-first-great-invention.
Edison's first great invention, http://www.history.com/this-day-in-history/edisons-first-great-invention (last visited May 20, 2013).
Edison's first great invention. The History Channel website. 2013. Available at: http://www.history.com/this-day-in-history/edisons-first-great-invention. Accessed May 20, 2013.