HANSEN, Johan P.; VYDRAL, Simon. Double points of compositions of projections. MATHEMATICA SCANDINAVICA, [S. l.], v. 58, p. 119–124, 1986. DOI: 10.7146/math.scand.a-12134. Disponível em: https://www.mscand.dk/article/view/12134. Acesso em: 5 dec. 2025.