YURTSUN, A. E. On the principles of counting the number of graphs. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 18, n. 5, p. 130–134, 1966. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/8452. Acesso em: 6 dec. 2025.