St. Augustine, Contra Faustum, XXII, 27 (PL 42:418).
St. Augustine, Sermones ad populum, LXI, 8 (PL 38:421).
St. Ambrose, De paradiso, VIII (PL 14:292).
St. Augustine, Retract., I, 9 (PL 32:596); cf. De libero arbitrio, III, 18 (PL 32:1295).
Glossa interlinearis, super Rom. 14:23 (VI:30r).
St. John Damascene, De fide orthodoxa, IV, 22 (PG 94:1199).
St. Thomas seems to be referring to St. Bonaventure, In Sent., II, 39, 1, 3 (QR II:906). However, the Quaracchi editors (scholion, ibid.) think that the difference is only verbal.
Aristotle, Ethica Nicomachea, VII, 9 (1151a 28 ff.).
In q. 17, aa. 1, 2.