Roberto Ortega-Martínez., C. J. Román-Moreno, and Ana Leonor Rivera. “The Wigner Function in Paraxial Optics I. Matrix Methods in Fourier Optics”. Revista Mexicana De Física, vol. 48, no. 6, Jan. 2002, pp. 565-0, https://rmf.smf.mx/ojs/index.php/rmf/article/view/3106.