J. C. Heesterman, ‘Ritual, Revelation and the Axial Age’, pp. 396–98; Heesterman, The Inner Conflict of Tradition: Essays on Indian Ritual, Kingship and Society (Chicago and London, 1985), p. 206; John Keay, India: A History (London, 2000), pp. 31–33; Thapar, Early India, pp. 126–30