Note
  1. Vedi J.J. Heckman, J. Stixrud e S. Urzua, The Effects of Cognitive and Noncognitive Abilities on Labor Market Outcomes and Social Behavior, in «Journal of Labor Economics», 24, 3, 2006, pp. 411-482; F. Cunha e J.J. Heckman, Formulating, Identifying and Estimating the Technology of Cognitive and Noncognitive Skill Formation, in «Journal of Human Resources», 43, 4, 2008; OECD, Skills for Social Progress: The Power of Social and Emotional Skills, OECD Skills Studies, Paris, OECD Publishing, 2015.