4. Knopoff, L., and Kagan, Y., 1977. Analysis of the theory of extremes as applied to earthquake problems, J. Geophys. Res., 82, 5647-5657.

Abstract from Harvard abstract service

Knopoff, L., and Kagan, Y., 1977. J. Geophys. Res., 82, 5647-5657, PDF file, 0.8 Mb.