Chávez-Alarcón, E., and J. Herrera-Velázquez. “Comparative Study Between Toroidal Coordinates and the Magnetic Dipole Field”. Revista Mexicana De Física E, vol. 57, no. 2 Jul-Dec, Jan. 2011, pp. 152-5, https://rmf.smf.mx/ojs/index.php/rmf-e/article/view/4670.