Costello, John R. (1992). The Periphrastic Duh Construction in Anabaptist and Nonsectarian Pennsylvania German: Synchronic and Diachronic Perspectives. In K. Burridge & W. Enninger (Eds.), Diachronic Studies on the Languages of the Anabaptists (pp. 242-263). Bochum: Brockmeyer.
