1. Adamiec P, Witaszek M, Witaszek K. Wear intensity of tyre steels (in Polish). Scientific Journals of the Silesian University of Technology. Series: Transport. 1998;30:71-78. http://delibra.bg.polsl.pl/Content/50419/BCPS-54956_1998_Intensywnosc-zuzycia.pdf.
2. Documentation of the 33WE electric traction unit maintenance system (in Polish). Bydgoszcz, 04.2013.
3. Documentation (Technical and Operating) of the Electric Multiple Unit Type 33WE. PESA, Bydgoszcz 2011.
4. Far M. Technical characteristics of the electric multiple unit type 33WE (in Polish). Institute of Rail Vehicles. Poznań 2011.
5. Firlik B, Staśkiewicz T. Challenges and opportunities of tram wheel profile design. Proceedings of the Fifth International Conference on Railway Technology: Research, Development and Maintenance. Montpellier 2022.08.22-25. https://www.ctresources.info/ccc/paper.html?id=9652.