ORIDOROGA, L. L. On representation of a scalar operator in the form of a sum of orthoprojections. Methods of Functional Analysis and Topology, [S. l.], v. 9, n. 3, p. 247–251, 2003. Disponível em: https://zen.imath.kiev.ua/index.php/mfat/article/view/219. Acesso em: 19 dec. 2025.