Frederick II (c. 995–1026), son of Thierry I of the House of Ardennes and Richilde von Blieskastel, daughter of Folmar III, Count in Bliesgau, was the count of Bar and duke of Lorraine, co-reigning with his father from 1019.
- The Geography of Power:Matilda of Tuscany and the Strategy of Active Defense, Valerie Eads, Crusaders, Condottieri, and Cannon: Medieval Warfare in Societies Around the Mediterranean, ed. Donald Joseph Kagay and L. J. Andrew Villalon, (Brill, 2003), 358.
- The Reform of the Church, J.P. Whitney, The Cambridge Medieval History, Vol. V, ed. J.R. Tanner, C.W. Previte-Orton, Z.N. Brooke, (Cambridge University Press, 1968), 23.
- The Reform of the Church, J.P. Whitney, The Cambridge Medieval History, Vol. V, 31.