ASHRAFI A.R.; MANOOCHEHRIAN B.; YOUSEFI-AZARI H. On the PI polynomial of a graph. Utilitas Mathematica , [S. l.], v. 71, 2006. Disponível em: https://utilitasmathematica.com/index.php/Index/article/view/399. Acesso em: 28 sep. 2026.