↑ Ripley's Believe it or Not, 2nd Series (Simon & Schuster, 1931); an updated reference is on page 140 of the Pocket Books paperback edition of 1948
↑ The New Big Book Of U.S. Presidents By Todd Davis, Marc Frey
↑ Randi Henderson and Tom Nugent, "The Zero Curse: More than just a coincidence?" (Reprinted from the Baltimore Sun), 2 tháng 11 năm 1980, in Syracuse Herald-American, p C-3
↑ "I'm not afraid. If I knew it was going to happen, I would go ahead and be President and do the best I could, for the last day I could."
