For an accessible summary description of the criteria, see W. Barnes Tatum, In Quest of Jesus: A Guidebook (Atlanta: Knox, 1982), pp. 76–77. For a more sustained discussion, see Norman Perrin, Rediscovering the Teaching of Jesus (New York: Harper & Row, 1967), pp. 15–49; Perrin seems to me to give too much priority to the criterion of dissimilarity.