Vargas, R., and M. Mosquera. “Phase Transitions in CaHPO$_4$ and BaHPO$_4$ above Room Temperature”. Revista Mexicana De Física, vol. 39, no. 3, Jan. 1992, pp. 450-5, https://rmf.smf.mx/ojs/index.php/rmf/article/view/2338.