Henry Peach Robinson (1869). “Pictorial Effect in Photography: Being Hints on Composition and Chiaro-oscuro for Photographers. To which is Added a Chapter on Combination Printing”, p.198
Edmund Burke (1790). “Reflections on the Revolution in France: And on the Proceedings in Certain Societies in London Relative to that Event. In a Letter Intended to Have Been Sent to a Gentleman in Paris”, p.230