1. E. Schuch, Ann der Physik, 13, 297–314, (1932).
2. Degussa, “Edelmetall-Taschenbuch,” Degussa, Frankfurt/Main, (1967).
3. V.L. Rideout and S. H. Wemple, J. Opt. Soc. Am., 56, 749–751, (1966).
4. O.S. Heavens, “Optical Properties of Thin Solid Films,” Academic Press, N. Y., (1955).