The Old Testament is frequently quoted, and often at great length. The Gospel is cited by name, usually that of Matthew, the other evangelists less often, and that of John least of all. The Acts of the Apostles and nearly all the Epistles are freely employed, including the Epistle to the Hebrews, but the Apocalypse is not cited. None of these could be named. Besides the "Didache", the "Didascalia" utilizes other ancient Christian documents as the Acts of Paul and the Gospel of Peter.