He specialized in the study of Athabascan languages, Chinookan languages, and Uto-Aztecan languages, producing important grammatical descriptions of Takelma, Wishram, Southern Paiute.
Dia mengkhususkan diri dalam studi bahasa Athabascan, bahasa Chinookan, dan bahasa Uto-Aztecan, memproduksi deskripsi tata bahasa penting dari Takelma, Wishram, Southern Paiute.