HEALY, Patrick; LYNCH, Karol. Building Blocks of Upward Planar Digraphs. Journal of Graph Algorithms and Applications, [S. l.], v. 11, n. 1, p. 3–44, 2007. DOI: 10.7155/jgaa.00135. Disponível em: https://jgaa.info/index.php/jgaa/article/view/paper135. Acesso em: 30 jun. 2024.