1. L. N. Bulaevskii, A. V. Zvarykina, Yu. S. Karimov, R. B. Lyobovskii, and I. F. Shchegolev, Zh. Eksp. Teor. Fiz. 62, 725 (1972) [Sov. Phys.-JETP 35, 384 (1972)].
2. I. F. Shchegolev, Phys. Status Solidi 12, 9 (1972).
3. L. J. Azevedo and W. G. Clark, Phys. Rev. B 16, 3252 (1977).
4. P. Delhaes, G. Keyrer, S. Flandrois, and J. P. Manceau, Phys. Stat. Solidi (b) 80, 125 (1977).
5. L. C. Tippie and W. G. Clark, Bull. Am. Phys. Soc. 22, 423 (1977), and to be published.