"John F. Kennedy: 1961 : containing the public messages, speeches, and statements of the president, January 20 to December 31, 1961" by John F. Kennedy, Washington: Office of the Federal Register, National Archives and Records Service, General Services Administration, 1962.
Joseph Butler (1856). “The analogy of religion, natural and revealed, to the constitution and course of nature: to which are added, two brief dissertations : On personal identity, and On the nature of virtue; and fifteen sermons”, p.404