Charlotte Bronte, Emily Bronte, Anne Bronte (2009). “The Bronte Sisters: Three Novels: Jane Eyre; Wuthering Heights; and Agnes Grey (Penguin Classics Deluxe Edition)”, p.592, Penguin
David Hume (1772). “An inquiry concerning human understanding. A dissertation on the passions. An. inquiry concerning the principles of morals. The natural history of religion”, p.5