1. D. M. Larsen and E. J. Johnson, in Proceedings of the 8th International Conference on Physics of Semiconductors, Kyoto, Japan, 1966 (Kyoto, 1966); J. Phys. Soc. Jpn., Suppl. 21, 443 (1966).
2. E. J. Johnson and D. M. Larsen, Phys. Rev. Lett. 16(15), 655 (1966).
3. D. M. Larsen, in Proceedings of the X International Conference on Physics of Semiconductors, Cambridge, MA, 1970, Ed. by S. P. Keller, J. C. Hensel, and F. Stern (US AEC, Oak Ridge, TN, 1970).
4. V. J. Ivanov-Omskii, L. I. Korovin, and E. M. Shereghii, Phys. Status Solidi B 90(1), 11 (1978).
5. NATO ASI Ser., Ser. B: Phys.;R. J. Nicholas,1990