Koshlyakov, V. N. “On Structural Transformations of Equations of Perturbed Motion for a Certain Class of Dynamical Systems”. Ukrains’kyi Matematychnyi Zhurnal 49, no. 4 (April 25, 1997): 535–539. Accessed April 16, 2025. https://umj.imath.kiev.ua/index.php/umj/article/view/5028.