Jeffrey Burton Russell, Dissent and Order in the Middle Ages: The Search for Legitimate Authority (New York: Twayne Publishers 1992), pp. 23 The Sermons of Martin Luther.
בדיקה אחרונה ב-13 בדצמבר 2010.  Jeffrey Burton Russell, Dissent and Order in the Middle Ages: The Search for Legitimate Authority (New York: Twayne Publishers 1992), pp. 23 The Sermons of Martin Luther II.