FILIPPOV, V.; RODIONOV, A. On the justification of the least square method for nonpotential, nonlinear operators. Pro Mathematica, [S. l.], v. 9, n. 17-18, p. 53–62, 1995. Disponível em: https://revistas.pucp.edu.pe/index.php/promathematica/article/view/10193. Acesso em: 23 dic. 2025.