1. E. Sailer, Phys. Status Solidi A 4, K173 (1971).
2. B. V. Shchepetil’nikov, A. I. Baranov, and L. A. Shuvalov, Fiz. Tverd. Tela (Leningrad) 29(3), 790 (1987) [Sov. Phys. Solid State 29 (3), 450 (1987)].
3. Y. Mugnier, C. Galez, J. M. Crettez, P. Bourson, and J. Bouillot, Solid State Commun. 115, 619 (2000).
4. L. G. Jacobsohn, P. Lunkenheimer, F. Laeri, U. Vietze, and A. Loidl, Phys. Status Solidi B 198, 871 (1996).
5. V. V. Vorob’ev, A. A. Kuleshov, E. V. Charnaya, A. A. Abramovich, S. V. Alchangyan, B. I. Kidyarov, and M. N. Kul’bitskaya, Fiz. Tverd. Tela (Leningrad) 31(1), 33 (1989) [Sov. Phys. Solid State 31 (1), 18 (1989)].