Cifuentes Rojas, William Andrés, et al. “Implementation of Pulse-Density Modulation PDM in an Ozone Generation System and Its Contribution to the Characteristic Efficiency Curve”. Revista Ingenierías Universidad De Medellín, vol. 13, no. 25, May 2015, pp. 137-49, doi:10.22395/rium.v13n25a9.