Friedrich Wilhelm Nietzsche, Aaron Ridley, Judith Norman (2005). “Nietzsche: The Anti-Christ, Ecce Homo, Twilight of the Idols: And Other Writings”, p.192, Cambridge University Press
"In 2012 interview, Pope Francis (then-Cardinal Bergoglio) reveals secret of celibacy". Interview with Rabbi Abraham Skorka, aleteia.org. March 18, 2013.
Saint John Chrysostom (1996). “A Select Library of the Nicene and Post-Nicene Fathers of the Christian Church: St. Chrysostom: On the priesthood; Ascetic treatises; Select homilies and letters; Homilies on the statutes”, Burns & Oates