Albert Einstein (2015). “Bite-Size Einstein: Quotations on Just About Everything from the Greatest Mind of the Twentieth Century”, p.32, St. Martin's Press
John Cotton Dana's remarks on a quotation suitable for inscription on a new building at Newark State College, Union, New Jersey (1912) as quoted in "The New York Times Book Review" (p. 55.), March 5, 1967.
Albert Einstein (2015). “Bite-Size Einstein: Quotations on Just About Everything from the Greatest Mind of the Twentieth Century”, p.32, St. Martin's Press