P. KOSTECKÝ, A. ONDRÁŠKOVÁ, S. ŠEVČÍK, L. ROSENBERG, and I. KOHÚT, “Observations of the anomalous third Schumann resonance peak during October 21 to 25, 2004 at Modra Observatory and a possible explanation”, Contrib. Geophys. Geod., vol. 35, no. 1, pp. 33-51, May 2021.