Darwin sends first three chapters of The Origin of Species to his publisher. (2013). The History Channel website. Retrieved 5:17, May 19, 2013, from http://www.history.com/this-day-in-history/darwin-sends-first-three-chapters-of-the-origin-of-species-to-his-publisher.
Darwin sends first three chapters of The Origin of Species to his publisher. [Internet]. 2013. The History Channel website. Available from: http://www.history.com/this-day-in-history/darwin-sends-first-three-chapters-of-the-origin-of-species-to-his-publisher [Accessed 19 May 2013].
“Darwin sends first three chapters of The Origin of Species to his publisher.” 2013. The History Channel website. May 19 2013, 5:17 http://www.history.com/this-day-in-history/darwin-sends-first-three-chapters-of-the-origin-of-species-to-his-publisher.
“Darwin sends first three chapters of The Origin of Species to his publisher,” The History Channel website, 2013, http://www.history.com/this-day-in-history/darwin-sends-first-three-chapters-of-the-origin-of-species-to-his-publisher [accessed May 19, 2013].
“Darwin sends first three chapters of The Origin of Species to his publisher,” The History Channel website, http://www.history.com/this-day-in-history/darwin-sends-first-three-chapters-of-the-origin-of-species-to-his-publisher (accessed May 19, 2013).
Darwin sends first three chapters of The Origin of Species to his publisher [Internet]. The History Channel website; 2013 [cited 2013 May 19] Available from: http://www.history.com/this-day-in-history/darwin-sends-first-three-chapters-of-the-origin-of-species-to-his-publisher.
Darwin sends first three chapters of The Origin of Species to his publisher, http://www.history.com/this-day-in-history/darwin-sends-first-three-chapters-of-the-origin-of-species-to-his-publisher (last visited May 19, 2013).
Darwin sends first three chapters of The Origin of Species to his publisher. The History Channel website. 2013. Available at: http://www.history.com/this-day-in-history/darwin-sends-first-three-chapters-of-the-origin-of-species-to-his-publisher. Accessed May 19, 2013.