Pandia Fajardo, Elma Alcira. “Pressure, State, Response Model (P-E-R) for the Classification of Environmental Indicators and Water Quality Management Case: Puyango Tumbes River Basin”. Revista Del Instituto De investigación De La Facultad De Minas, Metalurgia Y Ciencias geográficas, vol. 19, no. 37, July 2016, https://doi.org/10.15381/iigeo.v19i37.12953.