MAKAROV, V. L.; ROMANIUK, N. The FD-method for an eigenvalue problem in a case where the base problem has eigenvalues of arbitrary multiplicities in a Hilbert space . Reports of the National Academy of Sciences of Ukraine, Kyiv, Ukraine, n. 5, p. 26–34, 2015. DOI: 10.15407/dopovidi2015.05.026. Disponível em: https://nasu-periodicals.org.ua/index.php/dp/article/view/14971. Acesso em: 20 jun. 2026.