BANG, T. The theory of metric spaces applied to infinitely differentiable functions. MATHEMATICA SCANDINAVICA, [S. l.], v. 1, p. 137–152, 1953. DOI: 10.7146/math.scand.a-10374. Disponível em: https://www.mscand.dk/article/view/10374. Acesso em: 5 may. 2024.