ŁAZOR, Jerzy. Import and Export of Polish Coal in the Interwar Period. Kwartalnik Kolegium Ekonomiczno-Społecznego. Studia i Prace, [S. l.], n. 2, p. 33–48, 2017. DOI: 10.33119/KKESSiP.2017.2.2. Disponível em: https://econjournals.sgh.waw.pl/kwes/article/view/20. Acesso em: 16 kwi. 2024.