1. Falge, Jr. R.L.: Phys. Lett. A24, 579 (1967)
2. Lazarev, B.G., Sudovtsev, A.I., Smirnov, A.P.: J. Exp. Theor. Phys. (USSR)33, 1059 (1957): Sov. Phys. JETP6, 816 (1958)
3. Glover III, R.E., Moser, S., Baumann, F.: J. Low Temp. Phys.5, 519 (1971)
4. Yoshihiro, K., Glover III, R.E.: Proceedings of the 13th International Conference on Low Temperature Physics. Vol. 3, p. 547. New York: Plenum Press 1972
5. Lazarev, B.G., Kuz'menko, V.M., Sudovtsov, A.I., Mel'nikov, V.I.: Fiz. Metal. Metalloved.33, 984 (1972); Phys. Met. Metallogr. (USSR)35, 5, 78 (1972)