Mark Twain (2014). “Mark Twain on Common Sense: Timeless Advice and Words of Wisdom from America's Most-Revered Humorist”, p.37, Skyhorse Publishing, Inc.
Samuel Johnson, James Boswell (1825). “The Table Talk of Dr. Johnson: Comprising Opinions and Anecdotes of Life and Literature, Men, Manners, and Morals”, p.175