Sources:

• (2005) The Hindu Equilibrium: India C.1500 B.C. - 2000 A.D., Oxford University Press, p. xxxviii ISBN: 978-0-19-927579-3.
• Approximate boundaries are described by H.C. Raychaudhuri (p. 96-150), and https://books.google.com/books?id=8qvY8pxVxcwC&pg=PA386
• Habib, Irfan, and Habib, Faiz (1995). "A Map of India 600-320 B.C." in Proceedings of the Indian History Congress, vol. 56, pp. 95–104. www.jstor.org/stable/44158590
• Kenoyer, J. M. (1995), “Interaction Systems, Specialised Crafts and Culture Change: The Indus Valley Tradition and the Indo-Gangetic Tradition in South Asia”, in G. Erdosy, The Indo-Aryans of Ancient South Asia: Language, Material Culture, and Ethnicity, Berlin: Walter de Gruyter, ISBN 9783110144475
• Raychaudhuri, H.C. (1972), Political History of Ancient India: From the Accession of Parikshit to the Extinction of the Gupta Dynasty, Calcutta: University of Calcutta.
• Schwartzberg, J. E. (1992), A Historical Atlas of South Asia: University of Oxford Press
• Singh, U. (2009), A History of Ancient and Medieval India: From the Stone Age to the 12th Century, Delhi: Longman, ISBN 978-81-317-1677-9
• Background from http://www2.demis.nl/mapserver/mapper.asp