1. Häussler, P., Baumann, F.: Z. Phys. B49 (1983) 303.
2. Allen, J.F.: Philos. Mag. 16 (1933) 1005.
3. Meijer, H.C., Bots, G.J.C., Coops, G.M.: Proc. 6th Int. Cryog. Eng. Conf. (ICEC 6), Mendelssohn, K. (ed.), London: IPC Science and Technology Press, 1976, p. 404.
4. Compans, E., Baumann, F.: LT-18, Vol.1 (1987) 805.
5. Bankuti, J., Farkas, E.: Acta Phys. Acad. Sci. Hung. 50 (1981) 177.