GORBACHUK, M. L.; GORBACHUK, V. I. On the approximation to solutions of operator equations by the least squares method. Methods of Functional Analysis and Topology, [S. l.], v. 14, n. 3, p. 229–241, 2008. Disponível em: https://zen.imath.kiev.ua/index.php/mfat/article/view/387. Acesso em: 18 dec. 2025.