Pennsylvania miners perish in coal mine explosion. (2013). The History Channel website. Retrieved 6:45, May 23, 2013, from http://www.history.com/this-day-in-history/pennsylvania-miners-perish-in-coal-mine-explosion.
Pennsylvania miners perish in coal mine explosion. [Internet]. 2013. The History Channel website. Available from: http://www.history.com/this-day-in-history/pennsylvania-miners-perish-in-coal-mine-explosion [Accessed 23 May 2013].
“Pennsylvania miners perish in coal mine explosion.” 2013. The History Channel website. May 23 2013, 6:45 http://www.history.com/this-day-in-history/pennsylvania-miners-perish-in-coal-mine-explosion.
“Pennsylvania miners perish in coal mine explosion,” The History Channel website, 2013, http://www.history.com/this-day-in-history/pennsylvania-miners-perish-in-coal-mine-explosion [accessed May 23, 2013].
“Pennsylvania miners perish in coal mine explosion,” The History Channel website, http://www.history.com/this-day-in-history/pennsylvania-miners-perish-in-coal-mine-explosion (accessed May 23, 2013).
Pennsylvania miners perish in coal mine explosion [Internet]. The History Channel website; 2013 [cited 2013 May 23] Available from: http://www.history.com/this-day-in-history/pennsylvania-miners-perish-in-coal-mine-explosion.
Pennsylvania miners perish in coal mine explosion, http://www.history.com/this-day-in-history/pennsylvania-miners-perish-in-coal-mine-explosion (last visited May 23, 2013).
Pennsylvania miners perish in coal mine explosion. The History Channel website. 2013. Available at: http://www.history.com/this-day-in-history/pennsylvania-miners-perish-in-coal-mine-explosion. Accessed May 23, 2013.