ACKNOWLEDGMENTS
This research was partially supported by project grants TIN2010-21288-C02-01, TIN2009-13692-C03-03, and Santander-UCM GR 42/10, group reference 962022. Also, it is supported by the Spanish University Teacher Training Program (EDU/3445/2011). We also would like to thanks Rafael Fernández-López and Ángel Valero-Picazo by their invaluable contribution to the implementation of a previous version of Evaluators.