ORLOV, I.; BOZHONOK, E.; KUZMENKO, E. Necessary conditions for the K-extremum of a variational functional in Sobolev spaces over multi-dimensional domains . Reports of the National Academy of Sciences of Ukraine, Kyiv, Ukraine, n. 4, p. 19–24, 2025. DOI: 10.15407/dopovidi2014.04.019. Disponível em: https://nasu-periodicals.org.ua/index.php/dp/article/view/15773. Acesso em: 19 apr. 2026.