Agüeros, M., P. Casares-Hontanón, P. Coto-Millán, and M. Ángel Pesquera. “Technical Efficiency of the Generation of Knowledge in the European Union (2003-2010)”. Bulletin of Geography. Socio-Economic Series, no. 27, Feb. 2015, pp. 7-16, doi:10.1515/bog-2015-0001.