Romila Thapar (October 1971). “The Image of the Barbarian in Early India”. Comparative Studies in Society and History (Cambridge University Press) 13 (4): 408–436. JSTOR178208. "The stabilizing of what were to be the Arya-lands and the mleccha-lands took some time. In the Rg Veda the geographical focus was the sapta-sindhu (the Indus valley and the Punjab) with Sarasvati as the sacred river, but within a few centuries drya-varta is located in the Gariga-Yamfna Doab with the Ganges becoming the sacred river. (page 415)"