Sempiternus Rex: Encyclical Letter of Pope Pius XII, On the Fifteenth Centenary of the Council of Chalcedon; National Catholic Welfare Conference, 1951/0908, PGEN 132/5860. General Collection, GEN. University of Notre Dame Archives. https://archivesspace.library.nd.edu/repositories/2/archival_objects/1097527 Accessed November 29, 2024.