ZOPF, P. E. Variations in support burdens as measured by the dependency ratio. The Greek Review of Social Research, [S. l.], v. 19, p. 29–43, 1974. DOI: 10.12681/grsr.295. Disponível em: https://ejournals.epublishing.ekt.gr/index.php/ekke/article/view/6934. Acesso em: 19 apr. 2024.