1. Levshin, V.L., Zh. Fiz. Khim., 1931, vol. 2, p. 641
2. Blokhintsev, D.I., Zh. Eksp. Teor. Fiz., 1939, vol. 9, p. 459.
3. Stepanov, B.I., Dokl. Akad. Nauk SSSR, 1957, vol. 112, no. 5, p. 839.
4. Kirchhoff, G., Ann. Phys. Chem., 1860, vol. 109, p. 275.
5. van Roosbroeck, W. and Shockley, W., Phys. Rev., 1954, vol. 94, p. 1558.