Vereikina, M. B., & Sharkovsky, O. M. (1997). Tracing of pseudotrajectories of dynamical systems and stability of prolongations of orbits. Ukrains’kyi Matematychnyi Zhurnal, 49(8), 1016–1024. Retrieved from https://umj.imath.kiev.ua/index.php/umj/article/view/5096