Sekundærkilder Bachrach, Bernard S. (1972): . Minneapolis: University of Minnesota Press, ISBN 0-8166-0621-8. Geary, Patrick J. (1988): . Oxford: Oxford University Press, ISBN 0-19-504458-4. James, Edward (1991): . London: Blackwell, ISBN 0-631-14872-8. Oman, Charles (1908): . London: Rivingtons. Wallace-Hadrill, J. M. (1962): . London: Methuen. Wood, Ian N. (1994): . London: Longman, ISBN 0-582-21878-0.