1. V. N. Krivoruchko and T. E. Primak, Fiz. Tverd. Tela (Leningrad) 33, 3205 (1991) [Sov. Phys. Solid State 33, 1810 (1991)].
2. V. D. Buchel’nikov and V. G. Shavrov, Zh. Éksp. Teor. Fiz. 109, 706 (1996) [JETP 82, 380 (1996)].
3. S. V. Tarasenko, Opt. Spektrosk. 88, 310 (2000) [Opt. Spectrosc. 88, 272 (2000)].
4. S. V. Tarasenko, Opt. Spektrosk. 86, 658 (1999) [Opt. Spectrosc. 86, 588 (1999)].
5. S. V. Tarasenko, Opt. Spektrosk. 87, 1024 (1999) [Opt. Spectrosc. 87, 936 (1999)].