Galitzin Vertical Component Seismometer and McComb-Rombergtilt compensation seismograph in: Coming to grips with theEarthquake Problem, by Nicholas H. Heck, 1931. Journal of the FranklinInstitute, Vol. 212, No. 3, pp. 269-303.
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Date: 1930 ca.
Subject: Geophysics Seismology