GoletsV. L. “On the Problem of Disturbance of Stable Invariant Tore of the Dynamic System ”. Ukrains’kyi Matematychnyi Zhurnal 23, no. 1 (December 25, 1970): 130-137. Accessed November 24, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/8495.