HEDEN, Olof. Perfect Codes in Antipodal Distance-Transitive Graphs. Mathematica Scandinavica, Berkeley, CA, United States, v. 35, p. 29–37, 1974. DOI: 10.7146/math.scand.a-11532. Disponível em: https://journals.msp.org/mscand/article/view/2115. Acesso em: 25 jul. 2026.