1. Department of Didactics of Mathematics, Experimental and Social Sciences, University of the Basque Country (UPV/EHU), Donostia San Sebastián, Spain
2. Department of Didactics of Mathematics, Experimental and Social Sciences, University of the Basque Country (UPV/EHU), Leioa, Spain
3. Department of Didactics of Mathematics, Experimental and Social Sciences, University of the Basque Country (UPV/EHU), Vitoria-Gasteiz, Spain