1 THE APOSTLES OF THE SLAVS, Saints Cyril and Methodius, are remembered by the Church together with the great work of evangelization which they carried out. Indeed it can be said that their memory is particularly vivid and relevant to our day. Considering the grateful veneration enjoyed for centuries by the holy Brothers from Salonika (the ancient Thessalonica), especially among the Slav nations, and mindful of their incalculable contribution to the work of proclaiming the Gospel among those peoples; mindful too of the cause of reconciliation, friendly coexistence, human development and respect for the intrinsic dignity of every nation, by my Apostolic Letter Egregiae Virtutis of 31 December 1980 I proclaimed Saints Cyril and Methodius Co-Patrons of Europe. In this way I followed the path already traced out by my Predecessors, and notably by Leo XIII, who over a hundred years ago, on 30 September 1880, extended the cult of the two Saints to the whole Church, with the Encyclical Epistle Grande Munus, and by Paul VI, who, with the Apostolic Letter Pacis Nuntius of 24 October 1964, proclaimed Saint Benedict Patron of Europe.
Source: Slavorum Apostoli (Vatican.va)