OUATTARA, F. Relationship between geomagnetic classes’ activity phases and their occurrence during the sunspot cycle. Annals of Geophysics, [S. l.], v. 52, n. 2, p. 107–116, 2009. DOI: 10.4401/ag-4634. Disponível em: https://www.annalsofgeophysics.eu/index.php/annals/article/view/4634. Acesso em: 23 oct. 2021.