ANDERSEN, A. F. A Condition for $C$-Summability of Negative Order. MATHEMATICA SCANDINAVICA, [S. l.], v. 7, p. 337–346, 1959. DOI: 10.7146/math.scand.a-10579. Disponível em: https://www.mscand.dk/article/view/10579. Acesso em: 6 may. 2024.