Mazzarella, Adriano, and Andrea Giuliacci. “The El Niño Events: Their Classification and Scale-Invariance Laws”. Annals of Geophysics 52, no. 5 (May 25, 2009): 517–522. Accessed September 20, 2021. https://www.annalsofgeophysics.eu/index.php/annals/article/view/4607.