GONÇALVES, Daniel. Not all planar graphs are in PURE-4-DIR. Journal of Graph Algorithms and Applications, [S. l.], v. 24, n. 3, p. 293–301, 2020. DOI: 10.7155/jgaa.00533. Disponível em: https://jgaa.info/index.php/jgaa/article/view/paper533. Acesso em: 30 jun. 2024.