Elias, A. G., and N. Ortiz de Adler. “Forecast of Solar Maximum and Minimum Dates for Solar Cycles 23 to 29”. Annals of Geophysics 41, no. 1 (November 25, 1998). Accessed April 26, 2024. https://www.annalsofgeophysics.eu/index.php/annals/article/view/3790.