Poole, A. W. V., and M. Poole. “Long-Term Trends in F0 F2 over Grahamstown Using Neural Networks”. Annals of Geophysics 45, no. 1 (December 25, 2002). Accessed May 20, 2024. https://www.annalsofgeophysics.eu/index.php/annals/article/view/3485.