He has become known for his work on the proposed Dené–Yeniseian language family, seeking to establish that the Ket language of Siberia has a common linguistic ancestor with the Na-Dené languages of North America.
Acadou notoriedade por un seu traballo no que propón unha nova familia de linguas dené-ieniseianas, ao tentar estabelecer que a lingua ket de Siberia ten un antecesor lingüístico común coas linguas na-dené de América do Norte.