VENKATARAMAN, M. Spectral Theory in Hilbert Space. The Journal of the Indian Mathematical Society, [S. l.], v. 24, n. 3-4, p. 575–587, 1960. DOI: 10.18311/jims/1960/16934. Disponível em: http://informaticsjournals.com/index.php/jims/article/view/16934. Acesso em: 7 may. 2024.