I. Palacios, D. Ushiña, and D. Carrera, “Pixel Purity Index Applied to the Mapping of Degraded Soils by the Presence of Cangahuas in the Ilaló Volcano, Ecuador”, Int. J. Adv. Sci. Eng. Inf. Technol., vol. 11, no. 5, pp. 2121–2127, Oct. 2021.