^McKitterick, Rosamond; Luscombe, David; Fouracre, Paul; Reuter, Timothy; Riley-Smith, Jonathan; Abulafia, David; Allmand, C. T.; Jones, Michael (1995).
The New Cambridge Medieval History. Cambridge University Press. p. 472.
ISBN9780521414111.
^McKitterick, Rosamond; Luscombe, David; Fouracre, Paul; Reuter, Timothy; Riley-Smith, Jonathan; Abulafia, David; Allmand, C. T.; Jones, Michael (1995).
The New Cambridge Medieval History. Cambridge University Press. p. 472.
ISBN9780521414111.