1. Schwarz, Berthold E.: Ordeal by serpents, fire and strychnine.Psychiat. Quart., 34:3, 405–429, July 1960.
2. Williams, Harley: A Doctor Looks at Miracles. Roy. New York. 1959.
3. Jaspers, Karl: Quoted in: A Dictionary of Existentialism. Ralph B. Winn, compiler and arranger. Philosophical Library. New York. 1960.
4. Camus, Albert: The Myth of Sisyphus and Other Essays. Knopf. New York. 1955.
5. Sartre, Jean-Paul: Existentialism. Philosophical Library. New York. 1947.