Mehmood, M., S. Saleem, R. Filjar, N. A. Naqvi, and A. Ahmed. “Total Electron Content (TEC) Estimation over Pakistan from Local GPS Network Using Spherical Harmonics”. Annals of Geophysics, vol. 64, no. 1, Mar. 2021, p. GD102, doi:10.4401/ag-8433.