Duns Scotus (1266 - 1308 AD), Duns
Scoti Opera Omnia, vol XXIV, Liber 4, Dist. 25, Qu. 2, Paris 1894, pp. 367
-371.
Ricardus de Media Villa (13th century),
Super Quarto Sententiarum Dist. 25, a. 4, n.
1; ed. Bocatelli, Venice, 1499 (Pellechet-Polain, 10132/9920), f 177-R.