Tolong jelaskan mengenai Sumber dari Thuringi

Reuter, Timothy. Germany in the Early Middle Ages 800–1056. New York: Longman, 1991.

Thompson, James Westfall. Feudal Germany. 2 vol. New York: Frederick Ungar Publishing Co., 1928.

Schutz, Herbert. The Germanic Realms in Pre-Carolingian Central Europe, 400–750. American University Studies, Series IX: History, Vol. 196. New York: Peter Lang, 2000.