1. I.N. Kotel’nikov, A. Ya. Shul’man, D. K. Maude, et al., Pis’ma Zh. Éksp. Teor. Fiz. 60, 849 (1994) [JETP Lett. 60, 863 (1994)].
2. A. Ya. Shul’man and I. N. Kotel’nikov, in Proceedings of the 12th International Conference on High Magnetic Fields in Semiconductors (World Scientific, Singapore, 1997), p. 461.
3. I. N. Kotel’nikov and V. A. Volkov, in Proceedings of the 7th International Symposium “Nanostructures: Physics and Technology,” TP-07p (St. Petersburg, 1999), p. 272.
4. A. Petrou and B. D. McCombe, in Landau Level Spectroscopy, Ed. by G. Landwehr and E. I. Rashba (North-Holland, Amsterdam, 1991), Chap. 12, p. 679.
5. G. S. Boebinger, A. F. J. Levi, S. Schmitt-Rink, et al., Phys. Rev. Lett. 65, 235 (1990).