Whorf conducted important work on the Uto-Aztecan languages, which Sapir had conclusively demonstrated as a valid language family in 1915. Working first on Nahuatl, Tepecano, Tohono O'odham he established familiarity with the language group before he met Sapir in 1928. During Whorf's time at Yale he published several articles on Uto-Aztecan linguistics, such as "Notes on the Tübatulabal language". In 1935 he published "The Comparative Linguistics of Uto-Aztecan", and a review of Kroeber's survey of Uto-Aztecan linguistics. Whorf's work served to further cement the foundations of the comparative Uto-Aztecan studies.