John XXIII was a schismatic antipope in Italy 1410–1415, during the Western Schism. Eventually the Germans, English, and French demanded his abdication.
Antipope John XXIII. (2013). The Biography Channel website. Retrieved 06:01, May 23, 2013, from http://www.biography.com/people/antipope-john-xxiii-39264.
Antipope John XXIII. [Internet]. 2013. The Biography Channel website. Available from: http://www.biography.com/people/antipope-john-xxiii-39264 [Accessed 23 May 2013].
"Antipope John XXIII." 2013. The Biography Channel website. May 23 2013, 06:01 http://www.biography.com/people/antipope-john-xxiii-39264.
"Antipope John XXIII," The Biography Channel website, 2013, http://www.biography.com/people/antipope-john-xxiii-39264 [accessed May 23, 2013].
"Antipope John XXIII," The Biography Channel website, http://www.biography.com/people/antipope-john-xxiii-39264 (accessed May 23, 2013).
Antipope John XXIII [Internet]. The Biography Channel website; 2013 [cited 2013 May 23] Available from: http://www.biography.com/people/antipope-john-xxiii-39264.
Antipope John XXIII, http://www.biography.com/people/antipope-john-xxiii-39264 (last visited May 23, 2013).
Antipope John XXIII. The Biography Channel website. 2013. Available at: http://www.biography.com/people/antipope-john-xxiii-39264. Accessed May 23, 2013.