Glover, T. R. Conflict of Religions in the Early Roman Empire (2d ed., London, 1909).

Gruppe, G. Kulturgeschichte der römischen Kalserzeit (München, 1903-1904).[615]

Carter, J. B. Religion of Numa (London, 1906); The Religious Life of Ancient Rome (Boston and New York, 1911).

Reinach, S. Orpheus

Arnold, E. V. Roman Stoicism (Cambridge, England, 1911).

Etruscan

Herbig, G. Article "Etruscan Religion" (in Hastings's Encyclopædia of Religion and Ethics).

Celtic

Rhys, J. Celtic Heathendom (London, 1886).

Bertrand, A. Religion des Gaulois (2d ed., Paris, 1891).