ONDRÁŠKOVÁ, Adriena, Sebastián ŠEVČÍK, and Pavel KOSTECKÝ. “A significant Decrease of the Fundamental Schumann Resonance Frequency During the Solar Cycle Minimum of 2008-9 As Observed at Modra Observatory”. Contributions to Geophysics and Geodesy 39, no. 4 (December 1, 2009): 345–354. Accessed February 6, 2026. https://journal.geo.sav.sk/cgg/article/view/24.