Key points are not available for this paper at this time.
This research was funded by the Ministerio de Economia y Competitividad del Gobierno de Espana. References: PSI2011-28638, BES2012-053488. We would like to express our utmost gratitude to the Government of the Principality of Asturias (Spain), without whose collaboration this research would not have been possible. Finally, we would like to express our sincerest gratitude to the reviewers; their contributions have helped to improve considerably the final manuscript.
Fernández-Alonso et al. (2015) studied this question.