VlasenkoI. Yu. “Numerical Characteristics on the Set of Heteroclinic Points of Morse–Smale Diffeomorphisms on Surfaces”. Ukrains’kyi Matematychnyi Zhurnal 52, no. 10 (October 25, 2000): 1415-1420. Accessed November 24, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/4546.