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2. Fortunately there are substitutes for water otherwise our hydro-political futures would be impossible. In: ODA, Priorities for Water Resources Allocation and Management;Allan,1993
3. Overall perspectives on countries and regions;Allan,1994
4. Allen, R.G., Pereira, L.S., Raes, D.; Smith, M. (1998): Crop evapotranspiration—Guidelines for computing crop water requirements—FAO Irrigation and drainage paper 56. Food and Agriculture Organization, Rome, Italy.
5. Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas –CIEMAT- (2005): Análisis de ciclo de vida de los biocombustibles fase I. Análisis de Ciclo de Vida comparativo del etanol de cereales y de la gasolina. Ministerio de Medio Ambiente y Ministerio de Educación y Ciencia.