AKAMATSU, J., T. FURUZAWA, and K. IRIKURA, On the natures of the S-waves from local small earthquakes observed at Amagase Crustal Movement Observatory, Annu. Disast. Prev. Res. Inst., Kyoto Univ., 18-B, 11-21, 1975 (in Japanese).
AKI, K., Space and time spectra of stationary stochastic wave, with special reference to microtremors, Bull. Earthq. Res. Inst., 35, 415-456, 1957.
AKI, K. and P. G. RICHARDS, Quantitative Seismology, Theory and Methods, Vol. 1, W. H. Freeman and Company, San Francisco, California, 1980.