Charlotte Bronte, Emily Bronte, Anne Bronte (2009). “The Bronte Sisters: Three Novels: Jane Eyre; Wuthering Heights; and Agnes Grey (Penguin Classics Deluxe Edition)”, p.258, Penguin
Donald Knuth, Grady Booch, Linus Torvalds, Steve Wozniak, Vint Cerf (2011). “Leaders in Computing: Changing the Digital World”, p.44, BCS, The Chartered Institute
John Locke (1825). “An Essay Concerning Human Understanding: An analysis of Mr. Locke's Doctrine of ideas .... A defense of Mr. Locke's Opinion concerning personal identity .... A treatise on the conduct of the understanding. Some thoughts concerning reading and study for a gentleman. Elements of natural philosophy. A new method of a common place book. Extracted from the author's works. With a life of the author”, p.45