格拉哥里字母
Bulgarian students of the apostles Saints Cyril and Methodius, who were expelled from Great Moravia in 886, including Clement of Ohrid and Saint Naum, brought the Glagolitic alphabet to the First Bulgarian Empire and were received and accepted officially by Boris I of Bulgaria. He established two literary schools: the Preslav Literary School and the Ohrid Literary School. The Glagolitic alphabet was originally used at both schools, though the Cyrillic script was developed early on at the Preslav Literary School, where it superseded Glagolitic as official in Bulgaria in 893.