1. Bailey: Textbook of Histology. Eighth edition, The Williams and Wilkins Company, New York, 1932. (Pp. 310–314.)
2. Quoted in: Ormsby and Oliver: Diseases of the skin. Lea and Febiger, Philadelphia, 1937. (P. 32.)
3. Meirowsky, E.: Über das melanotischen Pigments der Haut und das Auges. Leipzig, 1908. (P. 92.)
4. McDonaugh, J. E. R.: Quoted in: Sutton, R. L.: Diseases of the Skin. C. V. Mosby Company, St. Louis, 1928. (P. 32.)
5. Dyson, W.:V. Ibid. Quoted in: Sutton, R. L.: