Vozniak, Oleh, and Valery Korobov. “Return Condition for Oscillating Systems”. Visnyk of V. N. Karazin Kharkiv National University. Ser. Mathematics, Applied Mathematics and Mechanics 101 (June 10, 2025): 5–20. Accessed February 1, 2026. https://periodicals.karazin.ua/mech_math/article/view/26500.