Méndez Sayago, J. M., and J. A. Méndez Sayago. “A Tradable Permit Systems for the Control of Pollution of Firms With Waste Water Discharges to the Sewerage Network”. Sociedad Y Economía, no. 18, Sept. 2011, pp. 241-67, https://sociedadyeconomia.univalle.edu.co/index.php/sociedad_y_economia/article/view/4171.