Flores Velásquez, P., P. Martínez de Anguita, R. Romero Calcerrada, C. J. Novillo, and M. A. Ruiz. “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, Vol. 17, no. 1, July 2008, pp. 39-53, doi:10.5424/srf/2008171-01022.