BazhuraB. P., and SamoilenkoA. M. “Investigation of a Dynamical System in a Neighborhood of an Invariant Toroidal Manifold in the General Case”. Ukrains’kyi Matematychnyi Zhurnal 46, no. 10 (October 25, 1994): 1399–1408. Accessed November 24, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/5620.