HANSEN, Sten. On configurations in 3-space without elementary planes and on the number of ordinary planes. Mathematica Scandinavica, Berkeley, CA, United States, v. 47, p. 181–194, 1980. DOI: 10.7146/math.scand.a-11884. Disponível em: https://journals.msp.org/mscand/article/view/1762. Acesso em: 25 jul. 2026.