PERRONE, L.; DE FRANCESCHI, G. Solar, ionospheric and geomagnetic indices. Annals of Geophysics, [S. l.], v. 41, n. 5-6, 1998. DOI: 10.4401/ag-3824. Disponível em: https://www.annalsofgeophysics.eu/index.php/annals/article/view/3824. Acesso em: 18 oct. 2021.