http://www.snopes.com/quotes/lincoln.asp "Pedigree for this quote is often asserted by pointing to the 1950 Lincoln Encyclopedia, compiled by...Shaw which 'authenticates' the quote by citing a purported letter from Lincoln to...found in Emanuel Hertz's 1931 book, Abraham Lincoln: A New Portrait. However, this source is fraudelent: Hertz was taken in by a forgery, and Shaw, a sloppy compiler, added the bogus letter."