HARARY, Frank; WILCOX, Gordon W. Boolean Operations on Graphs. MATHEMATICA SCANDINAVICA, [S. l.], v. 20, p. 41–51, 1967. DOI: 10.7146/math.scand.a-10817. Disponível em: https://www.mscand.dk/article/view/10817. Acesso em: 5 dec. 2025.