BRANSON, T. P. Differential operators cononically associated to a conformal structure. MATHEMATICA SCANDINAVICA, [S. l.], v. 57, p. 293–345, 1985. DOI: 10.7146/math.scand.a-12120. Disponível em: https://www.mscand.dk/article/view/12120. Acesso em: 5 may. 2024.