Woollcombe, K.J. "The Ministry and the Order of the Church in the Works of the Fathers" in The Historic Episcopate. Kenneth M. Carey (Ed.). Dacre Press (1954) p.31f
González, Justo L. (1984). The Story of Christianity: Vol. 1: The Early Church to the Reformation. San Francisco: Harper. ISBN0-06-063315-8.
Hastings, Adrian (1999). A World History of Christianity. Grand Rapids: Wm. B. Eerdmans Publishing. ISBN0-8028-4875-3.
Latourette, Kenneth Scott (1975). A History of Christianity, Volume 1: Beginnings to 1500 (edisi ke-revised). San Francisco: Harper. ISBN0-06-064952-6. (paperback).
The following links provide quantitative data related to Christianity and other major religions, including rates of adherence at different points in time: