Fonti a stampaFriderici Spanhemii F. De Papa Foemina Inter Leonem IV. & Benedictum III. Disquisitio Historica. - 1691
The Assumption of the Virgin, Pope St. Leo IV at left, detail of a9th-century fresco in the basilica of S. Clemente, Rome. [Unknown authorUnknown author / New Catholic Encycolopedia Vol.VI, P. 492 -- Public domain -- http://commons.wikimedia.org/wiki/File:Pope St. Leo IV.jpg]