Podogrodzka, Małgorzata. “Spatial Convergence of the Index of the Old Age in Poland”. Acta Universitatis Lodziensis. Folia Oeconomica 4, no. 324 (February 15, 2017): [51]-65. Accessed December 6, 2025. https://www.czasopisma.uni.lodz.pl/foe/article/view/553.