Vozniak, O. and Korobov, V. 2025. Return condition for oscillating systems. Visnyk of V. N. Karazin Kharkiv National University. Ser. Mathematics, Applied Mathematics and Mechanics. 101, (Jun. 2025), 5–20. DOI:https://doi.org/10.26565/2221-5646-2025-101-01.