1. Jarrett, James L. 1979.The Educational Theories of the Sophists, 1–110. New York: Columbia University Teachers College.
2. Moser, Shia. 1968.Absolutism and Relativism in Ethics, 3Springfield: Charles C. Thomas.
3. Berger, Peter L. and Luckmann, Thomas. 1966, 1967.The Social Construction of Reality, 5Garden City: Doubleday.
4. Kaufman, Gordon D. 1960.Relativism, Knowledge and Faith, 119Chicago: University of Chicago.
5. Westermarek, Edward. 1932.Ethical Relativity, 183–219. New York: Harcourt, Brace and Company.