"A red shield bearing two white crossed keys, and surmounted by the tiara, is to be seen in a window of the cathedral of Bourges accompanying the achievements of the anti-popesClement VII and Benedict XIII, and other examples of these tinctures are to be found in manuscripts dating from the time of the former of these anti-popes and from that of Nicholas V, in a series of shields painted on the ceiling formerly in the church of San Simone at Spoleto (ca. 1400), in the 15th-century glass in the cathedrals of York and of Carpentras, in various 15th-century books of arms both English, German, and Italian, as well as in Martin Schrot's book of arms which is as late as 1581." Donald Lindsay Galbreath, A Treatise on Ecclesiastical Heraldry (W. Heffer and Sons, 1930).
""Froissart, in his Chronicles referring to the events of the year 1383, is the first to blazon the arms of the Church: faisait Vevesque de Mordwich porter devant lui les armes de I'Eglise, la bannière de St. Pierre, de gueules à deux clefs d'argent en sautoir, comme Gonfanonnier du Pape Urbain." Donald Lindsay gules, A Treatise on Ecclesiastical Heraldry (W. Heffer and Sons, 1930)
