EKHOLM, T. Immersions in the metastable range and spin structures on surfaces. MATHEMATICA SCANDINAVICA, [S. l.], v. 83, n. 1, p. 5–41, 1998. DOI: 10.7146/math.scand.a-13840. Disponível em: https://www.mscand.dk/article/view/13840. Acesso em: 2 may. 2024.