Singh, Birbal, and Devbrat Pundhir. “Shift of Effective Lightning Areas During Pre to Post Period of Solar Cycle Minimum of 2008-2009 As Determined from Schumann Resonance Studies at Agra, India”. Annals of Geophysics, vol. 57, no. 6, Mar. 2015, https://doi.org/10.4401/ag-6596.