Jaworski, Jacek, and Olga Szlachetka. “Free Vibrations of Cantilever Bars With Linear and Nonlinear Variable Cross-Section”. Discontinuity, Nonlinearity, and Complexity, vol. 6, no. 4, Aug. 2026, pp. 489-01, https://doi.org/10.5890/DNC.2017.12.007.