1. Frey, W., Huss, R., Seidel, H., and Werkman, E., Phys. Status Solidi B, 1975, no. 68, p. 257.
2. Krutikov, F.V., Silkin, N.I., and Stepanov, V.G., Fiz. Tverd. Tela, 1975, vol. 17, no. 11, p. 3363.
3. Krutikov, F.V., Silkin, N.I., and Stepanov, V.G., Fiz. Tverd. Tela, 1976, vol. 18, no. 10, p. 2958.
4. Krutikov, F.V., Silkin, N.I., and Stepanov, V.G., Paramagnitnyi rezonans (Paramagnetic Resonance), Kazan: Kazan Gos. Univ., 1978, nos. 10–11, p. 113.
5. Krutikov, F.V., Silkin, N.I., and Stepanov, V.G., Paramagnitnyi rezonans (Paramagnetic Resonance), Kazan: Kaazan Gos. Univ., 1978, no. 13, p. 79.