Pope Pelagius I

"Among these [councils] I wish above all to follow and imitate the one whom we know to have been the author of the Council of Chalcedon, and who, in accordance with his name, clearly showed himself to be a member of that lion [Pope Leo I] who came forth from the tribe of Judah, with his lively zeal and faith. (from the encyclical letter Vas electionis, 444)"

"It has never been permitted, nor will it ever be permitted, for a particular synod to be convened to judge a general council. **from the letter Relegentes autem, 447."

"Heinrich Denzinger, Enchiridion Symbolorum, bilingual edition edited by Peter Hünermann, Italian version edited by Angelo Lanzoni and Giovanni Zaccherini, Edb, 2001."