Cross-correlation earthquake precursors in the hydrogeochemical and geacoustic signals for the Kamchatka peninsula,
Ryabinin, G. V., Yu. S. Polyakov, V. A. Gavrilov, and S.~F.~Timashev (2012),
Acta Geophysica, 60, 3, 874,
10.2478/s11600-012-0031-y.