MAKHKAMOV, K. Sh. On the exact degree of complexity of a class of operator equations of the second kind in a Hilbert space. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 46, n. 7, p. 893–903, 1994. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/5681. Acesso em: 7 apr. 2025.