 Innocent III refers to no less than nine methods of falsification.From the thirteenth century on to January, 1909 it sufficed, in order to give a papal document legal force, to post it up at Rome on the doors of St. Peter's, of the Lateran, the Apostolic Chancery and in the Piazza del Campo di Fiori, but since they acquired force only by publication in the Acta Apostolicae Sedis.In the modern period also, papal letters have been constantly issued, but they proceed from the popes themselves less frequently than in the Middle Ages and Christian antiquity; most of them are issued by the papal officials, of whom there is a greater number than in the Middle Ages, and to whom have been granted large delegated powers, which include the issuing of letters.