TRALLI, G. Double ball property: an overview and the case of step two Carnot groups. Bruno Pini Mathematical Analysis Seminar, [S. l.], v. 3, n. 1, p. 33–47, 2012. DOI: 10.6092/issn.2240-2829/3417. Disponível em: https://mathematicalanalysis.unibo.it/article/view/3417. Acesso em: 25 apr. 2024.