SAMOILENKO, Yu. S.; TUROWSKA, L. B. On bounded and unbounded idempotents whose sum is a multiple of the identity. Methods of Functional Analysis and Topology, [S. l.], v. 8, n. 1, p. 79–100, 2002. Disponível em: https://zen.imath.kiev.ua/index.php/mfat/article/view/179. Acesso em: 18 dec. 2025.