Columbia subject headings:
Gregory I, Pope, approximately 540-604.
Popes--Correspondence.
Rescripts, Papal--History.
Harvard subject headings:
Gregory I, Pope, approximately 540-604
Rescripts, Papal.
Princeton subject headings:
Catholic Church--History--Sources.
Gregory I, Pope, approximately 540-604.
Rescripts (Canon law)
Rescripts, Papal--History.