Mark Twain (2014). “Mark Twain on Common Sense: Timeless Advice and Words of Wisdom from America's Most-Revered Humorist”, p.9, Skyhorse Publishing, Inc.
George Bernard Shaw (2015). “George Bernard Shaw: Collected Articles, Lectures, Essays and Letters: Thoughts and Studies from the Renowned Dramaturge and Author of Mrs. Warren’s Profession, Pygmalion, Arms and The Man, Saint Joan, Caesar and Cleopatra, Androcles And The Lion”, p.418, e-artnow