González Gómez, M., Polomé, P. and Prada Blanco, A. (2011) “Specifications and sampling considerations in estimated demand for an area of outstanding natural beauty: The Illas Cíes in Galicia”., Economía Agraria y Recursos Naturales - Agricultural and Resource Economics, 1(2), pp. 67–92. doi: 10.7201/earn.2001.02.04.