1. Mees, C. E. K. and James, T. H. (Eds), “The Theory of the Photographic Process”, 3rd Edition, p. 149, The Macmillan Co., New York (1966).
2. Stevens, G. W. W., in Mees, C. E. K. (Ed), “The Theory of the Photographic Process”, 2nd Edition, p. 253, The Macmillan Co., New York (1954)
3. Ref. 1, Ch. 6. p. 123 and Ch. 8, p. 153.
4. Ref. 1, p. 154.