Mikhailov, A. V., B. A. de la Morena, G. Miro, and D. Marin. “A Method for f0F2 Monitoring over Spain Using the El Arenosillo Digisonde Current Observations”. Annals of Geophysics 42, no. 4 (November 25, 1999). Accessed December 2, 2021. https://www.annalsofgeophysics.eu/index.php/annals/article/view/3748.