Rovai, Emanuel silva, et al. “Evaluation of Dental Staining Using a Dentifrice Containing Chlorhexidine and Zinc Acetate. A Doble Blind Randomized Clinical Trial”. Brazilian Dental Science, vol. 16, no. 2, June 2013, pp. 51-58, doi:10.14295/bds.2013.v16i2.884.