KOMOROWSKI, T.; WOSKO, J. A remark on the retracting of a ball onto a sphere in an infinite dimensional Hilbert space. MATHEMATICA SCANDINAVICA, [S. l.], v. 67, p. 223–226, 1990. DOI: 10.7146/math.scand.a-12334. Disponível em: https://www.mscand.dk/article/view/12334. Acesso em: 5 may. 2024.