^Fryde, E. B.; Greenway, D. E.; Porter, S.; Roy, I. (1996). Handbook of British Chronology (Third revised ed.). Cambridge, UK: Cambridge University Press. p. 220. ISBN0-521-56350-X.
^The Wiley-Blackwell encyclopedia of Anglo-Saxon England (Second ed.). Chichester, West Sussex: Wiley Blackwell. 2014. p. 551. ISBN978-0-470-65632-7.