1. See, for example, Laser in Physical Chemistry and Biophysics ed. by J.Joussot-Dubien (Elsevier Scientific Publ.Co.,Amster dam, 1975)
2. A notable exception occurs when the molecule is kept at very low temperature (a few degree °K). See, for example, L. A. Bykovskaya, R.I. Personov and B.M. Kharlamov, Chem.Phys. Letters 27, 80 (1974)
3. C.A. Sacchi, O. Svelto and G. Prenna, Histochemical Journal 6, 251 (1974)
4. S. Cova, G. Prenna, C.A. Sacchi, and O. Svelto, in Excited States of Biological Molecules ed. by J.B. Birks, pp.223–232 (Wiley-Interscience, New York, 1975)
5. A. Albert: The Acridines, 2 nd ed. (Edward Arnold Publishers Ltd, London, 1966) .