Ma, M., a-Mendieta., J. Oliveros-Oliveros, E. Teniza-Tetlalmatzi, and J. Vargas-Ubera. “Hermitian Operators and Boundary Conditions”. Revista Mexicana De Física, vol. 58, no. 1, Jan. 2012, pp. 94-103, https://rmf.smf.mx/ojs/index.php/rmf/article/view/3889.