Polyakov, Andrey. “On Homogeneous Controllability Functions”. Visnyk of V. N. Karazin Kharkiv National University. Ser. Mathematics, Applied Mathematics and Mechanics 94 (November 29, 2021): 24-39. Accessed June 17, 2024. https://periodicals.karazin.ua/mech_math/article/view/18003.