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Content.- Principles of the Application of Seismo-Acoustics to Coal Seams Subject to Rock Bursts.- SED Electrodynamic Geophones.- Impulse Method for Calibration of Electrodynamic Vibrometers.- Simple Piezoelectric Accelerometer Geophones for Geophysical Laboratory Investigations.- Audiometric Location of Lost Boreholes in Mine Workings.- The ZUA-2-VCh Seismo-Acoustic Equipment.- Automatic Monitor for Natural Seismo-Acoustic Pulses.- A Two-Coil Galvanometer for Modulation with a Very-Low-Frequency Amplifier.- Seismo-Acoustic Determination of the Boundaries of Zones in Coal Seams Subject to Rock.