DIJKSMA, A.; DE SNOO, H. S. Symmetric and selfadjoint relations in Krein spaces II. Annales Fennici Mathematici, [S. l.], v. 12, n. 2, p. 199–216, 1987. DOI: 10.5186/aasfm.1987.1208. Disponível em: https://afm.journal.fi/article/view/134597. Acesso em: 25 nov. 2024.