Letter from the field of Waterloo in June 1815. "The Fifteen Decisive Battles of the World: From Marathon to Waterloo" by Edward Shepherd Creasy, 1851.
Arthur Wellesley, Duke of Wellington (2012). “Maxims and Opinions of Field-Marshal His Grace the Duke of Wellington, Selected From His Writings and Speeches During a Public Life of More Than Half a Century”, p.377, tredition