A publication or announcement issued directly by the Pope or by an official delegated by him. Matters of faith and morals were generally the subjects of these letters, designated as decreta. Others of more dogmatic importance were commonly called epistolae tractoriae. They were incorporated in collections of canon law and ranked with canons of synods in importance. Gratian and other canonists insisted that every papal letter of general character was authoritative for the entire Church. There were many forged papal letters during the Middle Ages. From the thirteenth to the twentieth centuries a papal document was given legal form by posting it on the doors of St. Peter's, the Lateran, or the Apostolic Chancery and in the Piazza del Campo di Fiori. Now they acquire force by publication in the Acta Apostolocae Sedis. These papal writings are published in a variety of forms, e.g., apostolic letters, constitutions, rescripts, bulls, and briefs. The original letters are deposited in the roman archives. Private collections of papal letters also exist.