Erwin R. Goodenough, Jewish Symbols in the Greco-Roman Period, 13 vols. (New York: Pantheon, 1953), vol. 2, pp. 258f., and vol. 3, pp. 1116–1117; Campbell Bonner, Studies in Magical Amulets, Chiefly Graeco-Egyptian (Ann Arbor: Univ. of Michigan Press, 1950), p. 148ff., 291, n. 227.