C. L. Fajardo Hoyos, A. M. Gómez Sánchez, and J. I. Sarmiento Castillo, “Variables associated to sales income behavior in the main market squares of Popayán, Colombia”, Semest. Econ., vol. 21, no. 49, pp. 115–145, Oct. 2018, doi: 10.22395/seec.v21n49a5.