LOKAZIUK, O. Lie symmetries of linear systems of two second-order ordinary differential equations. Reports of the National Academy of Sciences of Ukraine, Kyiv, Ukraine, n. 5, p. 3–11, 2021. DOI: 10.15407/dopovidi2021.05.003. Disponível em: https://nasu-periodicals.org.ua/index.php/dp/article/view/2021-5-1. Acesso em: 18 apr. 2026.