PETUNIN, Yu. I. On the concept of generalized solution of operator equations in banach spaces. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 48, n. 9, p. 1286–1290, 1996. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/5242. Acesso em: 5 dec. 2025.