Zuccheretti, E., G. Tutone, U. Sciacca, C. Bianchi, and J. A. Baskaradas. “The New AIS-INGV Digital Ionosonde”. Annals of Geophysics 46, no. 4 (December 25, 2003): 647–659. Accessed October 25, 2021. https://www.annalsofgeophysics.eu/index.php/annals/article/view/4377.