David Ricardo, John Ramsay McCulloch (1846). “The Works of David Ricardo, Esq., M.P.: With a Notice of the Life and Writings of the Author”, p.388, London, J. Murray
Booker T. Washington (1904*). “Address of Booker T. Washington, Principal of the Tuskegee Normal & Industrial Institute: Before the National Educational Association, St. Louis, Missouri, June 30, 1904”