ZATORSKY, R.A.; PYLYPIV, V.M.; GULKA, S. On some related enumeration problems. Carpathian Mathematical Publications, [S. l.], v. 5, n. 2, p. 242–248, 2013. DOI: 10.15330/cmp.5.2.242-248. Disponível em: https://journals.pnu.edu.ua/index.php/cmp/article/view/1315. Acesso em: 28 apr. 2024.