Mitropolsky , Yu. O., I. O. Antonishin, A. K. Prikarpatsky, and V. G. Samoilenko. 1992. “Simplex Analysis of Dynamical Systems With a Perturbation. New Criteria of Stabilization of a Homoclinic Separatrix and Its Use”. Ukrains’kyi Matematychnyi Zhurnal 44 (1), 46-66. https://umj.imath.kiev.ua/index.php/umj/article/view/2319.