Regesta pontificium Romanorum : ab condita ecclesia ad annum post Christum natum MCXCVIII - Ewald, Paul, 1857-1911; Jaffe, Philipp, 1819-1870; Kaltenbrunner, F.; Loewenfeld, S.; Wattenbach, Wilhelm, 1819-1897 (Lipsiae : Veit, 1885)