HANSEN, Johan P.; VYDRAL, Simon. Double points of compositions of projections. Mathematica Scandinavica, Berkeley, CA, United States, v. 58, p. 119–124, 1986. DOI: 10.7146/math.scand.a-12134. Disponível em: https://journals.msp.org/mscand/article/view/1498. Acesso em: 25 jul. 2026.