Cook, Arthur B.: Zeus: a study in ancient religion (Band 2,2): Zeus god of the dark sky (thunder and lightning): Appendixes and index (Cambridge, 1925)

Bronze medallion of Commodus,
struck 185 A.D. (Gnecchi Medagl.
Rom. ii. 59 f. no. 74 pi. 83, 2).
Supra p. 1209 n- 2-