Charles Dickens (1867). “Charles Dickens's works. Charles Dickens ed. [18 vols. of a 21 vol. set. Wanting A child's history of England; Christmas stories; The mystery of Edwin Drood].”, p.4
Albert Einstein (2016). “The Albert Einstein Collection: Essays in Humanism, The Theory of Relativity, and The World As I See It”, p.10, Open Road Media