LUDWIKOWSKI, Rett Ryszard. Welfare state a opportunity state. Czasopismo Prawno-Historyczne, [S. l.], v. 24, n. 2, p. 143–173, 1972. Disponível em: https://pressto.amu.edu.pl/index.php/cph/article/view/50741. Acesso em: 12 luty. 2026.