Pizani, Andréia Mara Andrade, et al. “Dental Bleaching Agents With Calcium and Their Effects on Enamel Microhardness and Morphology”. Brazilian Journal of Oral Sciences, vol. 14, no. 2, July 2015, pp. 154-8, https://periodicos.sbu.unicamp.br/ojs/index.php/bjos/article/view/8640831.