"In order to account for this fact, we are bound to assume that the language of the original population of the towns of Central Asia, where Indo-Iranians must have arrived in the second millennium BCE, on the one hand, and the language spoken in the Punjab, the homeland of the Indo-Aryans, on the other, were intimately related."
January 1, 1970
https://en.wikiquote.org/wiki/Alexander_Lubotsky