1. A. I. Lebedev, Fiz. Tverd. Tela (St. Petersburg) 51(2), 341 (2009) [Phys. Solid State 51 (2), 362 (2009)].
2. A. I. Lebedev, Fiz. Tverd. Tela (St. Petersburg) 51(4), 757 (2009) [Phys. Solid State 51 (4), 802 (2009)].
3. A. I. Lebedev, Fiz. Tverd. Tela (St. Petersburg) 51(11), 2190 (2009) [Phys. Solid State 51 (11), 2324 (2009)].
4. H. Tabata, H. Tanaka, and T. Kawai, Appl. Phys. Lett. 65, 1970 (1994).
5. B. D. Qu, M. Evstigneev, D. J. Johnson, and R. H. Prince, Appl. Phys. Lett. 72, 1394 (1998).