G K Chesterton, John Bunyan, Brother Lawrence, Andrew Murray, R A Torrey (2013). “Hendrickson Christian Classics Audio Library”, p.18, Hendrickson Publishers
St. Augustine, Dr. Howard Taylor, Mrs. Howard Taylor, Apostolic Fathers, J. Oswald Sanders (2010). “Moody Classics Complete Set: Includes 19 Classics of the Faith in a Single Volume”, p.1542, Moody Publishers
Saint Augustine of Hippo, Saint Augustine, Thomas A'Kempis (2006). “The Confessions of St. Augustine, Including the Imitation of Christ”, p.217, Cosimo, Inc.