Fryde, E. B.; Greenway, D. E.; Porter, S.; Roy, I. (1996). Handbook of British Chronology (Third revised ed.). Cambridge: Cambridge University Press. ISBN0-521-56350-X.
Story, Joanna (2003). Carolingian Connections: Anglo-Saxon England and Carolingian Francia, c. 750-870. Aldershot, UK: Ashgate. ISBN0-7546-0124-2.