John Buchan (2016). “The Complete Works of John Buchan (Unabridged): Thriller Classics, Spy Novels, Supernatural Tales, Short Stories, Poetry, Historical Works, The Great War Writings, Essays, Biographies & Memoirs – All in One Volume”, p.1672, e-artnow
David Hume (1826). “The history of England: From the invasion of Julius Caesar to the revolution of 1688 : To which is prefixed a short account of his life, written by himself”, p.187