Sparavalo , M. K. “Stability and Controllability of Motion of Dynamic Systems at a Distance from the Equilibrium Positions ”. Ukrains’kyi Matematychnyi Zhurnal 44, no. 8 (September 8, 1992): 1145–1149. Accessed December 5, 2025. https://umj.imath.kiev.ua/index.php/umj/article/view/8051.