J. Robert Oppenheimer's letter to his brother Frank Oppenheimer (March 12, 1932), as quoted in "Robert Oppenheimer: Letters and Recollections" edited by Alice Kimball Smith (p. 155), 1995.
Thomas Jefferson, Henry Augustine Washington (1854). “The Writings of Thomas Jefferson: Being His Autobiography, Correspondence, Reports, Messages, Addresses, and Other Writings, Official and Private : Published by the Order of the Joint Committee of Congress on the Library, from the Original Manuscripts, Deposited in the Department of State”, p.390