James M. Robinson, “The Sayings of Jesus: ‘Q’,” Drew Gateway (Fall 1983); Helmut Koester, Ancient Christian Gospels: Their History and Development (Philadelphia: Trinity Press International, 1990); John Kloppenborg, The Formation of Q (Philadelphia: Fortress, 1987); Arland Jacobsen, The First Gospel (Missoula: Polebridge, 1992); Burton Mack, Q—The Lost Gospel (San Francisco: HarperSan Francisco, 1993).