Geological
Institute, Bulgarian Academy of Sciences
Section Seismology, Earth Tides and Gravimetry, Department Reference Systems and Geodynamics, Royal Observatory of Belgium
Istituto Nazionale di Geofisica e Vulcanologia, Italy
European Center for Geodynamics and Seismology (Walferdange, Luxembourg)
GEOPHYSICAL OBSERVATORY -Plovdiv
International Lithosphere Program Task Group II-5 Earthquake Recurrence Through Time