1 WHO Collaborating Centre for Research in Education and Health, Université Clermont Auvergne, Chamalières 63400, France; UNESCO Chair Global Health & Education Research Group, Université Clermont Auvergne, Chamalières 63400, France.
2 WHO Collaborating Centre for Research in Education and Health, Université Clermont Auvergne, Chamalières 63400, France; UNESCO Chair Global Health & Education Research Group, Université Clermont Auvergne, Chamalières 63400, France; UNESCO Chair Global Health & Education Research Group, University of Huddersfield, Huddersfield, UK. Electronic address: n.j.gray@hud.ac.uk.