In the version of this article originally published, the names of three authors were incorrect. The authors were listed as \"Coral Fustero-Torres\", \"Elena Pineiro\" and \"Melchor Sánchez-Martínez\". Their respective names are \"Coral Fustero-Torre\", \"Elena Piñeiro-Yáñez\" and \"Melchor Sanchez-Martinez\". The errors have been corrected in the print, HTML and PDF versions of this article.