Keller, Dawid. “Polish State Railways in 1945–1989 – A Research Contribution”. Studia Historiae Oeconomicae 39, no. 1 (December 1, 2021): 216–249. Accessed May 4, 2024. https://pressto.amu.edu.pl/index.php/sho/article/view/sho-2021-0009.