Friedrich Nietzsche, Maudemarie Clark, Brian Leiter (1997). “Nietzsche: Daybreak: Thoughts on the Prejudices of Morality”, p.226, Cambridge University Press
"Human, All Too Human: A Book for Free Spirits". Book by Friedrich Nietzsche, transl. by Helen Zimmern, Section IX, "Man Alone with Himself"/ aphorism 633, 1909-1913.