↑ Easterling, P. E. (1997). The Cambridge Companion to Greek Tragedy. Cambridge University Press. p. 352. ISBN 978-0-521-42351-9. Retrieved 19 November 2017.
↑ James Rachels, The Legacy of Socrates: Essays in Moral Philosophy Columbia University Press, 2007 ISBN 0-231-13844-X Accessed November 24, 2017