SIQINQIMUGE; JIRIMUTU; LINGQI, ZHAO. On the gracefulness of the digraphs n - C→19 for even n. Utilitas Mathematica , [S. l.], v. 85, 2011. Disponível em: https://utilitasmathematica.com/index.php/Index/article/view/780. Acesso em: 8 may. 2026.