1. A. S. Borovik-Romanov and M. P. Orlova, Sov. Phys. JETP 4, 531 (1956).
2. A. S. Borovik-Romanov, Sov. Phys. JETP 9, 539 (1959).
3. A. S. Borovik-Romanov and E. G. Rudashevskii, Sov. Phys. JETP 20, 1407 (1964).
4. A. S. Borovik-Romanov, in Problems of Magnetism, Collection of Articles (Nauka, Moscow, 1972), p. 47 [in Russian].
5. I. Bernal, C. W. Struck, and J. G. White, Acta Crystallogr. 16, 849 (1963).