^McManners, Oxford Illustrated History of Christianity (2002), pp. 37–38, Chapter 1 The Early Christian Community subsection entitled "Rome", quote: "The 'synod' or, in Latin, 'council' (the modern distinction making a synod something less than a council was unknown in antiquity) became an indispensable way of keeping a common mind, and helped to keep maverick individuals from centrifugal tendencies. During the third century synodal government became so developed that synods used to meet not merely at times of crisis but on a regular basis every year, normally between Easter and Pentecost."
^McManners, Oxford Illustrated History of Christianity (2002), p. 37, Chapter 1 The Early Christian Community subsection entitled "Rome", quote: "In Acts 15 scripture recorded the apostles meeting in synod to reach a common policy about the Gentile mission."