1. Stanworth, J. E., J. Soc. Glass Tech., 30, 54 (1946); 32, 154 and 366 (1948); Glastech. Ber., 23, 297 (1950).
2. Pauling, L., “The Nature of the Chemical Bond” (Cornell Univ. Press, 1940).
3. Berzelius, J. J., Ann. Phys. Chem., 32, 577 (1834).
4. Lenher, V., and Wolesensky, E., J. Amer. Chem. Soc., 35, 718 (1913).
5. Using the relation between cation radius and partial refractivity of oxides in glass: Stanworth, J. E., J. Soc. Glass Tech., 32, 154 (1948); “Physical Properties of Glass”, 62 (Oxford: Clarendon Press, 1950).