Berezansky Y.М. and Konstantinov , A.Y. (1992) “Multiparametric spectral problems as expanded by the author’s own vectors ”, Ukrains’kyi Matematychnyi Zhurnal, 44(7), pp. 901–913. Available at: https://umj.imath.kiev.ua/index.php/umj/article/view/8122 (Accessed: 6 December 2025).