Columbia subject headings:
Bulgaria--Church history--Congresses.
Bŭlgarska pravoslavna t︠s︡ŭrkva--History--Congresses.
Cyril, Saint, Apostle of the Slavs, approximately 827-869--Congresses.
Methodius, Saint, Apostle of the Slavs, approximately 825-884 or 885--Congresses.
Orthodox Eastern Church--Bulgaria--History--Congresses.
Harvard subject headings:
Cyril, Saint, Apostle of the Slavs, approximately 827-869.
Methodius, Saint, Apostle of the Slavs, approximately 825-884 or 885.
Princeton subject headings: