Career
His work on the Caucasian languages includes Der Kaukasus und seine Völker (The Caucasus and Its Peoples. 1887); Die Sprachen des kaukasischen Stammes (The Languages of the Caucasian Tribes. 1895); and Wanderungen und Siedelungen der germanischen Stämme in Mitteleuropa (Migration and Settlement of the Germanic Tribes in Central Europe.