Anderle Milan, Appeltans P., Čelikovský Sergej, Michiels W., Vyhlídal T. :  Controlling the variable length pendulum: Analysis and Lyapunov based design methods , Journal of the Franklin Institute-Engineering and Applied Mathematics vol.359, 3 (2022), p. 1382-1406 [2022] Download DOI: 10.1016/j.jfranklin.2021.11.026