John Ruskin, Charles Eliot Norton, John Lewis Bradley, Ian Ousby (1987). “The Correspondence of John Ruskin and Charles Eliot Norton”, p.59, Cambridge University Press
John Ruskin (1800). “The Seven Lamps of Architecture: Also, Lectures on Architecture and Painting; The Study of Architecture; Sesame and Lilies; Unto this Last; The Queen of the Air; The Storm-cloud of the Nineteenth Century”