FORTUNA, E.; GALBIATI, M. A counterexample to the seperation of semialgebraic sets. MATHEMATICA SCANDINAVICA, [S. l.], v. 69, p. 161–165, 1991. DOI: 10.7146/math.scand.a-12374. Disponível em: https://www.mscand.dk/article/view/12374. Acesso em: 4 may. 2024.