Richard Gerberding, The New Cambridge Medieval History : Volume 1, C.500-c.700, Cambridge University Press, , 979 p. (ISBN978-0-521-36291-7, lire en ligne), p.17 ; In 235 the army murdered the last of the Severans, Severus Alexander (222–235), and it was as if the dam broke. For the next fifty years the army put up twenty-six emperors and then murdered almost all of them
