First astronauts introduced. (2013). The History Channel website. Retrieved 2:43, May 23, 2013, from http://www.history.com/this-day-in-history/first-astronauts-introduced.
First astronauts introduced. [Internet]. 2013. The History Channel website. Available from: http://www.history.com/this-day-in-history/first-astronauts-introduced [Accessed 23 May 2013].
“First astronauts introduced.” 2013. The History Channel website. May 23 2013, 2:43 http://www.history.com/this-day-in-history/first-astronauts-introduced.
“First astronauts introduced,” The History Channel website, 2013, http://www.history.com/this-day-in-history/first-astronauts-introduced [accessed May 23, 2013].
“First astronauts introduced,” The History Channel website, http://www.history.com/this-day-in-history/first-astronauts-introduced (accessed May 23, 2013).
First astronauts introduced [Internet]. The History Channel website; 2013 [cited 2013 May 23] Available from: http://www.history.com/this-day-in-history/first-astronauts-introduced.
First astronauts introduced, http://www.history.com/this-day-in-history/first-astronauts-introduced (last visited May 23, 2013).
First astronauts introduced. The History Channel website. 2013. Available at: http://www.history.com/this-day-in-history/first-astronauts-introduced. Accessed May 23, 2013.