Warrington, E. Michael, Alain Bourdillon, Eulalia Benito, Cesidio Bianchi, Jean-Philippe Monilié, Martha Muriuki, Marco Pietrella, et al. “Aspects of HF Radio Propagation”. Annals of Geophysics 52, no. 3-4 (April 25, 2009): 301–321. Accessed May 13, 2026. https://www.annalsofgeophysics.eu/index.php/annals/article/view/4577.