1. Blodgett, K. B., Phys. Rev., 55, 391 (1939).
2. Taylor, H. D., "The Adjustment and Testing of Telescope Objectives" (York: T. Cooke, 1896).
3. Jones, F. L., and Homer, H. J., J. Op. Soc. Amer., 31, 34 (1941).
4. Nicoll, F. H., RCA Review, 6, 287 (1942).
5. British Patent No. 538272.