1. Goldman, M.: Spin Temperature and Nuclear Magnetic Resonance in Solids, p. 342. Clarendon Press, Oxford (1970)
2. Wahlqist, H.: Chem. Phys. 35, 1708–1710 (1961)
3. Smith, G.W.: Appl. Phys. 35, 1217–1221 (1964)
4. Atsarkin, V.A.: Zh. Exp. Teor. Fiz. 64, 1086–1095 (1973)
5. Atsarkin, V.A., Riabushkin, O.A.: Zh. Exp. Teor. Fiz. 17, 103–105 (1973)