Robert Holzmann, Mercedes Ayuso, and Jorge Miguel Bravo. 2017. “On the Heterogeneity in Longevity Among Socioeconomic Groups: Scope, Trends, and Implications for Earnings-Related Pension Schemes”. Global Journal of Human-Social Science 17 (E1):31-57. https://socialscienceresearch.org/index.php/GJHSS/article/view/1961.