Daniel J. Harrington, The Gospel of Matthew (Collegeville, Minnesota: Liturgical Press, 1991), 384–387.
G. F. Hill, "Coins and Medals (Western)," in James Hastings and John A. Selbie, (eds.), Encyclopedia of Religion and Ethics, Part 6 (Whitefish, Montana: Kessinger Publishing, 2003), 703.
Johannes A. Mol, Klaus Militzer, and Helen J. Nicholson, The Military Orders and the Reformation: Choices, state building, and the weight of tradition (Hilversum: Uitgeverij Verloren, 2006), 287.
Piero Della Francesca, Enigma of Piero, (2nd ed., trans. Martin Ryle and Kate Soper; London: Verso Books, 2001), 68.
