Skup, Z. “Forced Vibration of a Nonlinear Stationary System With a Friction Clutch, Structural Friction Being Taken Into Consideration”. Engineering Transactions 39, no. 3-4 (December 31, 1991): 369–387. Accessed January 17, 2026. http://et.ippt.gov.pl/index.php/et/article/view/1632.