Pope Pelagius I writes to patrician John regarding the detrimental consequences of the schism within the Church (the so-called Three Chapters Controversy), especially concerning the recent election of a schismatic patriarch of Aquileia, urging the Byzantine official not to recognize their authority as they had not been canonically elected.
Pope Pelagius I writes to patrician Valerian, beseeching him to repress the schismatics and support the quest to restore union to the Church.
Pope Pelagius I writes to a patrician John on the detrimental effects of the schism in the Church (the so-called Three Chapters Controversy), singling out Bishop Euphrasius as a particularly depraved schismatic and advising the patrician to repress the schismatics in the province of Aquileia (that is, the region Venetia et Histria).
Pope Pelagius I writes to patrician Valerian, urging him to take action against the schismatic bishops in the ecclesiastical provinces of Milan and Aquileia and support the papal quest to bring back unity to the Church.
Pope Pelagius I writes to patrician Narses, beseeching him to take action against the schismatic bishops, namely the bishop of Fossombrone and the bishops of Liguria, Venetia and Istria.
Pope Pelagius I writes to Charles, the magister militum, regarding the Schism of the Three Chapters and the schismatic bishops.
Pope Pelagius II writes to Helias, the patriarch of Aquileia, and all the bishops of Istria, the province whose prelates still persevered in their refusal to condemn the three chapters denounced by the Fifth Ecumenical Council (Constantinople II) of 553, urging them to desist from their schismatic ways and return to the embrace of the Catholic Church.
Pope Gregory I writes to Severus, the patriarch of Aquileia, requesting on behalf of the emperor (Maurice) that he come to Rome with his clergy and be judged on a synod (for his unwillingness to condemn the Three Chapters and his perseverance in supporting the schism).
Pope Gregory I writes to Callinicus, the Exarch of Italy, regarding a variety of affairs, including the recent military victory over the Slavs and the return of the Church of Koper to the Catholic creed.
Pope Gregory I writes to Maxim, the bishop of Salona, on a variety of matters, including the latest advances of the Slavs and their recent incursions into Italy by way of Istria.
Pope Honorius incites all the bishops of the ecclesiastical province Venetia et Histria to profess disobedience to the deposed patriarch Fortunatus of Grado and to accept subdeacon Primogenius, to whom the pope had already sent the pallium, as their new lawful head of the ecclesiastical province; moreover, the pope promises to open diplomatic negotiations with the Lombard king, with whom the deposed Fortunatus sought refuge, with the goal of restoring all the ecclesiastical goods stolen by the said Fortunatus.
Pope Adrian I writes to Charlemagne, the King of the Franks and the Lombards, beseeching him to direct Duke Marcarius of Friuli to help reinstate the Istrian bishop Maurice – whose eyes have been gouged out by “the most abominable Greeks” – to his bishopric.
Pope Sergius III writes to John, the bishop of Pula, informing him of Archbishop of Ravenna John XI's complaints against Count Albuin, who unlawfully alienated the possessions of the Church of Ravenna in Istria, and asking him to personally convey to the Count that he must return these possessions under the threat of excommunication and that King Berengar I will not be crowned emperor until he grants Albuin’s March (of Istria or of Friuli) to someone better.
Pope Gregory VII admonishes a noble knight Wezelin for attacking Dalmatia, ruled by a ruler approved by the Holy See, and orders him to immediately stop with the hostilities lest the "sword of St. Peter" be unleashed upon him and his followers.