1. Plato. Philebus. 1997. Translated by Frede, Dorothea. In Plato: Complete Works, ed. J.M. Cooper. Indianapolis: Hackett.
2. Plato. Republic. 1997. Translated by Grube, G.M.A. Revised by Reeve, C.D.C. In Plato: Complete Works, ed. J.M. Cooper. Indianapolis: Hackett.
3. Foley, R. 2008. Plato’s Undividable Line: Contradiction and Method in Republic VI. Journal of the History of Philosophy 46 (1): 1–23.
4. Giaquinto, Marcus. 2007. Visual Thinking in Mathematics: An Epistemological Study. Oxford: Oxford University Press.
5. ———. 2008. Visualizing in Mathematics. In The Philosophy of Mathematical Practice, ed. Paolo Mancosu. New York: Oxford University Press.