Tozzi, R., and A. De Santis. “Detecting Geomagnetic Field Nonlinearities by Bispectral Analysis and a Phase Coupling Nonlinear Technique”. Annals of Geophysics 45, no. 2 (December 25, 2002). Accessed April 20, 2024. https://www.annalsofgeophysics.eu/index.php/annals/article/view/3514.