1. A. Abragam and B. Bleaney, Electron Paramagnetic Resonance of Transition Ions (Clarendon, Oxford, 1970; Mir, Moscow, 1973).
2. V. N. Vasyukov, S. N. Lukin, and G. A. Tsintsadze, Fiz. Nizk. Temp. 10, 742 (1984) [Sov. J. Low Temp. Phys. 10, 390 (1984)].
3. S. N. Lukin, Fiz. Tverd. Tela (Leningrad) 33(1), 47 (1991) [Sov. Phys. Solid State 33, 25 (1991)].
4. S. N. Lukin, Fiz. Tverd. Tela (Leningrad) 31(8), 244 (1989) [Sov. Phys. Solid State 31, 1415 (1989)].
5. K. P. Lee and D. Walsh, Can. J. Phys. 49, 1620 (1971).