KROM, M. R. The Decision Problem for Segregated Formulas in First-Order Logic. MATHEMATICA SCANDINAVICA, [S. l.], v. 21, p. 233–240, 1967. DOI: 10.7146/math.scand.a-10862. Disponível em: https://tidsskrift.dk/math/article/view/10862. Acesso em: 14 aug. 2026.