"Encouragement of Science". J. Robert Oppenheimer's address at Science Talent Institute (March 6, 1950), as quoted in "Bulletin of the Atomic Scientists", Volume 7, No. 1 (pp. 6-8), January 1951.
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