1. See the recent reviews of P. A. Beck, Met. Trans. 2, 2015 (1971); R. Tournier, L. T. 13, Boulder, Colorado, 1972, edit. K. D. Timmerhaus, W. J. O’sullivan and E. F. Hammel, (Plenum, New York 1974), vol. 2, p. 257; J. A. Mydosh, AIP Conf. Proc. 24, 131 (1974); J. P. Perrier and J. L. Tholence, J. Phys. (Paris) 35, C4, 163 (1974).
2. See for example N. Rivier and K. Adkins, Amorphous Magnetism, edit. H. O. Hooper and A. M. de Graaf (Plenum, New York 1973), p. 215; S. F. Edwards and P. W. Anderson, J. Phys. F 5, 966 (1975).
3. J. L. Tholence and R. Tournier, J. Phys. (Paris), 35, C4, 229 (1974).
4. A. Amamou, R. Caudron, P. Costa, J. M. Friedt, F. Gautier and B. Loegei, L. T. 14, Otaniemi, Finland, 1975, edit. M. Krusius and M. Vuorio, (North Holland, Amsterdam), (1975), vol. 3, p. 254, and to be published in J. Phys. F.
5. J. Souletie and R. Tournier, J. Low Temp. Phys. 1, 95 (1969) and ref. therein.