KIRCHHEIM, B.; SERRA CASSANO, F. Rectifiability and parameterization of intrinsic regular surfaces in the Heisenberg group. ANNALI SCUOLA NORMALE SUPERIORE - CLASSE DI SCIENZE, [S. l.], v. 3, n. 4, p. 871-896, 2009. DOI: 10.2422/2036-2145.2004.4.07. Disponível em: http://20.103.181.36/index.php/annaliscienze/article/view/59. Acesso em: 28 may. 2025.