A few things can be established with certainty, others with a good degree of likelihood, and yet others remain entirely uncertain.

quoted in Philology and the historical interpretation of the Vedic texts, in: Bryant, E. F., & Patton, L. L. (2005). The Indo-Aryan controversy : evidence and inference in Indian history. Routledge. page 297 . quoted in Elst, Koenraad (2007). Asterisk in bharopiyasthan: Minor writings on the Aryan invasion debate.