From 1937, he collaborated with Whorf on historical-comparative Azteco-Tanoan languages, but further planned collaboration was cut short by Whorf's death in 1941.
Desde 1937, colaborou con Benjamin Whorf en estudos historico-comparados das linguas azteco-tanoanas, pero o traballo que tiñan planeado viuse interrompido pola morte de Whorf en 1941.