Torres del Castillo, G., D. Rosete Álvarez, and I. Fuentecilla Cárcamo. “The Action of Canonical Transformations on Functions Defined on the Configuration Space”. Revista Mexicana De Física, vol. 56, no. 2, Jan. 2010, pp. 113-0, https://rmf.smf.mx/ojs/index.php/rmf/article/view/3736.