PARKKONEN, J.; PAULIN, F. A classification of $\mathbb{C}$-Fuchsian subgroups of Picard modular groups. MATHEMATICA SCANDINAVICA, [S. l.], v. 121, n. 1, p. 57–74, 2017. DOI: 10.7146/math.scand.a-26128. Disponível em: https://www.mscand.dk/article/view/26128. Acesso em: 19 oct. 2021.