Adams, John P. (2010). "Sede Vacante 1304–1305". csun.edu. Northridge, CA: California State University (published 7 January 2016). Archived from the original on 11 February 2016. Retrieved 11 February 2016.
Adams, John P. (2010). "Sede Vacante 1304–1305". csun.edu. Northridge, CA: California State University (published 7 January 2016). Archived from the original on 11 February 2016. Retrieved 11 February 2016.
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One or more of the preceding sentences incorporates text from a publication now in the public domain: Kirsch, Johann Peter (1912). "Unam Sanctam". In Herbermann, Charles (ed.). Catholic Encyclopedia. Vol. 15. New York: Robert Appleton Company.