Flores Velásquez, P., P. Martínez de Anguita, R. Romero Calcerrada, C. J. Novillo, and M. A. Ruiz. 2008. “Payment for Environmental Services Between the Adding and the Subsidization: Application to the Valuation of the Landscape in the San Juan Dam, Madrid, Spain”. Forest Systems 17 (1), 39-53. https://doi.org/10.5424/srf/2008171-01022.