SORVALI, T. The boundary mapping induced by an isomorphism of covering groups. Annales Fennici Mathematici, [S. l.], n. 526, 1973. DOI: 10.5186/aasfm.1973.526. Disponível em: https://afm.journal.fi/article/view/134182. Acesso em: 26 nov. 2024.