MOURGOVA, Mariana. Demographic Ageing of the Population in Bulgaria. European Journal of Social Science Education and Research, London, U.K., v. 4, n. 1, p. 64–75, 2017. DOI: 10.26417/ejser.v6i2.p216-224. Disponível em: https://revistia.com/index.php/ejser/article/view/365. Acesso em: 4 apr. 2025.