Pérez-Salas, R., T. M, R. Aceves, R. Rodríguez -Mijangos, and M. Barboza-Flores. “Optical Vibronic Spectra of Aggregates in Eu$^{\mathbf2+}$ -Doped KCl and KBr Crystals”. Revista Mexicana De Física, vol. 49, no. 2, Jan. 2003, pp. 102-0, https://rmf.smf.mx/ojs/index.php/rmf/article/view/3139.