John Locke (1824). “The Works of John Locke: Essay concerning human understanding (concluded) Defence of Mr. Locke's opinion concerning personal identity. Of the conduct of the understanding. Some thoughts concerning reading and study for a gentlemen. Elements of natural philosophy. New method of a common-place-book”, p.356
Robert Browning, Elizabeth Barrett Browning (2009). “The Letters of Robert Browning and Elizabeth Barrett Browning: 1845-1846”, p.9, The Floating Press