1. Herzberg, G., The Spectra of Diatomic Molecules, 409 (van Nostrand, 1950).
2. Förster, Th., and Kasper, K., Z. Elektrochem., 59, 977 (1955).
3. Förster, Th., paper presented at the Fifth European Symposium on Molecular Spectroscopy, Amsterdam (1961).
4. Stevens, B., and Hutton, E., Nature, 186, 1045 (1960).
5. Bandow, F., Z. physik. Chem., 196, 329 (1951). Berg, N., and Norden, G., Acta Path. Microbiol. Scand., 36, 193 (1955).