REUTER, G. E. H. A note on contraction semigroups. MATHEMATICA SCANDINAVICA, [S. l.], v. 3, p. 275–280, 1955. DOI: 10.7146/math.scand.a-10446. Disponível em: https://www.mscand.dk/article/view/10446. Acesso em: 3 jul. 2024.