de Jong, Mayke (1995). "Carolingian monasticism: the power of prayer". In McKitterick, Rosamond (ed.). The New Cambridge Medieval History. Cambridge: Cambridge University Press. pp. 622.
Fouracre, Paul (1995). "Frankish Gaul of 814". In McKitterick, Rosamond (ed.). The New Cambridge Medieval History. Cambridge: Cambridge University Press. pp. 88–90, 91.