1. A. Bril, in Kallman and Spruch, Luminescence of Organic and Inorganic Materials, Wiley, New York, 479 (1962).
2. See e.g. G.F.J. Garlick, Chapter 12 in Luminescence of Inorganic Solids (P. Goldberg, ed.), Academic Press, New York (1966).
3. A. Bril and W.L. Wanmaker, J. Electrochem. Soc. 111, 1363 (1964).
4. A. Bril, W.L. Wanmaker and J. Broos, J. Chem. Phys. 43, 311 (1975).
5. G. Blasse, W.L. Wanmaker and J.W. ter Vrugt, J. Electrochem. Soc. 115, 673 (1968).