Columbia subject headings:
Christian literature, Early--History and criticism--Congresses.
Gregory I, Pope, approximately 540-604--Congresses.
Harvard subject headings:
Christian literature, Early--History and criticism--Congresses.
Gregory I, Pope, approximately 540-604--Congresses.
Princeton subject headings:
Christian literature, Early--History and criticism--Congresses.
Gregory I, Pope, approximately 540-604--Congresses.