John Ruskin (1855). “Notes on Some of the Principal Pictures Exhibited in the Rooms of the Royal Academy, the Old and New Societies of Painters in Water Colours, the Society of British Artists and the French Exhibition”, p.11
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”
John Ruskin (1872). “The Political Economy of Art: Being the Substance (with Additions) of Two Lectures Delivered at Manchester, July 10th and 13th, 1857”, p.114