LINGQI, ZHAO; YUANSHENG, YANG; WEI, FENG; YUAN, REN; JINGJING, BAO. On the gracefulness of the digraph P→a,b. Utilitas Mathematica , [S. l.], v. 101, 2016. Disponível em: https://utilitasmathematica.com/index.php/Index/article/view/1143. Acesso em: 7 may. 2026.