Makarov, V.L. and Romaniuk, N. 2025. 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. 5 (Feb. 2025), 26–34. DOI:https://doi.org/10.15407/dopovidi2015.05.026.