1. C. Jacker, Window on the Unknown, a History of the Microscope, Charles Scribner’s Sons, New York, N. Y. 10017 (1966).
2. S. H. Gage, Brief history of lenses and microscopes, in The Microscope, 17th ed., Comstock Publishing Associates, Ithaca, N. Y. 14850 (1947).
3. Milestones in Optical History (booklet of paintings), Bausch and Lomb Optical Co. Rochester, N. Y. 14602 (1954).
4. I. Asimov, Biographical Encyclopedia of Science and Technology, Doubleday and Co., Garden City, N. Y. 11533 (1972).
5. L. van Puyvelde, Les Primitifs Flamands, Editions Marion, Bruxelles, Belgium (1947). See plates 12 and 13, and introductory notes, p. 18, indicating that eyeglasses were in use in 1530.