Bkz. testimonia DK 68 A 80, DK 68 A 37 and DK 68 A 43. Ayrıca bkz. Cassirer, Ernst (1953). An Essay on Man: an Introduction to the Philosophy of Human Culture. Doubleday & Co. s. 214. ASINB0007EK5MM.
Tatarkiewicz, Wladyslaw (2006). J. Harrell; C. Barrett; D. Petsch (Ed.). History of Aesthetics. A&C Black. s. 89. ISBN0826488552. Erişim tarihi: 6 Mayıs 2015.