Sekundære Alexander, Archibald; Lagarde, André; Turmel, Joseph (1915): , C. Scribner's Sons. Bauer, Susan Wise (2010): , W.W. Norton. Brubaker, Leslie; Haldon, John F. (2011): . Cambridge University Press, ISBN 978-0-521-43093-7. Bury, J.B. (2015): . Cambridge University Press. ISBN 9781108083188. Garland, Lynda (1998): , Taylor and Francis. Herrin, Judith (2001): . London: Phoenix Press. ISBN 1-84212-529-X.