Catholic Encyclopedia: Sts. Cyril and Methodius - Also called Constantine and Methodius. Biography of these ninth-century brothers, Apostles of the Slavs. Lives of the Saints: SS Cyril and Methodius - From Alban Butler's Lives of the Saints. Slavorum Apostoli - Commemoration of the Eleventh Centenary of the Evangelizing Work of SS. Cyril and Methodius. Encyclical of Pope John Paul II, promulgated in 1985. Cyril and Methodius, Missionaries to the Slavs - Outline of their missionary activities. With prayer in traditional and contemporary language. Grande Munus - Encyclical of Pope Leo XIII, on SS. Cyril and Methodius, promulgated in 1880. Catholic Online: Sts. Cyril and Methodius - Reflection on their lives. St. Cyril and St. Methodius - The story of these two brothers, suitable for children.