“A Study of Geomagnetic Field and It’s Secular Variation at the Location Brazilian Anomaly (25°S, 45°W)”. Ibn AL-Haitham Journal For Pure and Applied Sciences, vol. 21, no. 1, Sept. 2017, pp. 27-34, https://jih.uobaghdad.edu.iq/index.php/j/article/view/1370.