1. R. T. Williams, Semicond. Insul.,3, 251–283 (1978).
2. M. Ueta, Y. Kondo, M. Hirai, and T. Yoschinari, J. Phys. Soc. Jpn.,30, No. 2, 440–498 (1971).
3. T. Karasawa and M. Hirai, J. Phys. Soc. Jpn.,39, No. 4, 999–1003 (1975).
4. V. M. Lisitsyn, V. I. Korepanov, and V. Yu. Yakovlev, Izv. Vyssh. Uchebn. Zaved., Fiz., No. 11, 5–29 (1996).
5. V. M. Lisitsyn and V. Yu. Yakovlev, Fiz. Tverd. Tela,37, No. 4, 1126–1133 (1995).