M. Duszek and T. Łodygowski, “Тhе Post-Yield Analysis of Rigid Plastic Beams Columns and Frames”, Eng. Trans., vol. 33, no. 1-2, pp. 173–203, Jun. 1985, Accessed: Jan. 17, 2026. [Online]. Available: http://et.ippt.gov.pl/index.php/et/article/view/1841