SORVALI, T. On the dilatation of isomorphisms between covering groups. Annales Fennici Mathematici, [S. l.], n. 551, 1973. DOI: 10.5186/aasfm.1973.551. Disponível em: https://afm.journal.fi/article/view/134207. Acesso em: 25 nov. 2024.