Makarov VL, 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 . Dopov. Nac. akad. nauk Ukr. [Internet]. 2025 Feb. 3 [cited 2026 Apr. 18];(5):26-34. Available from: https://nasu-periodicals.org.ua/index.php/dp/article/view/14971