Torres del Castillo, G., and T. Tepper García. “Supersymmetry and the Constants of Motion of the Two-Dimensional Isotropic Harmonic Oscillator”. Revista Mexicana De Física, vol. 48, no. 1, Jan. 2002, pp. 16-0, https://rmf.smf.mx/ojs/index.php/rmf/article/view/3026.