Mark Twain (2014). “Mark Twain on Common Sense: Timeless Advice and Words of Wisdom from America's Most-Revered Humorist”, p.16, Skyhorse Publishing, Inc.
Henry Ward Beecher, Augusta Moore (1859). “Notes from Plymouth Pulpit: A Collection of Memorable Passages from the Discourses of Henry Ward Beecher, with a Sketch of Mr. Beecher and the Lecture Room”, p.57