5. Kagan, Y., and Knopoff, L., 1978. Statistical study of the occurrence of shallow earthquakes, Geophys. J. R. astr. Soc., 55, 67-86.

Abstract from Blackwell Synergy

Kagan, Y., and Knopoff, L., 1978. Geophys. J. R. astr. Soc., 55, 67-86, PDF file, 1.3 Mb.