NEUMAN, F. Functional and differential equations. Annales Universitatis Paedagogicae Cracoviensis Studia Mathematica, [S. l.], v. 1, p. 109–116, 2001. Disponível em: https://studmath.uken.krakow.pl/article/view/13521. Acesso em: 30 oct. 2026.