RUDENOK, Alexander E.; VASILEVICH, Mikhail N. About isochrons of strong focus. Journal of the Belarusian State University. Mathematics and Informatics, [S. l.], n. 2, p. 16–29, 2025. DOI: 10.33581/2520-6508-2025-2-16-29. Disponível em: https://journals.bsu.by/index.php/mathematics/article/view/6685. Acesso em: 1 oct. 2026.