"Benedict V", Encyclopedia Britannica (1910), Vol. 3, p. 718.
"Benedict V", Encyclopedia Americana (1918), p. 504.
Society for the Diffusion of Useful Knowledge. (1835). "Benedict V,"Penny cyclopaedia, Vol. 4, p. 214; excerpt, "By several writers he is considered only as an intruder, but in the late Papal chronologies published in Italy we find him placed among the regular popes."
newadvent.org
"List of Popes,"Catholic Encyclopedia (2009); retrieved 2011-11-02.