Columbia subject headings:
Church and state.
Leo I, Pope, -461--Correspondence.
Harvard subject headings:
Church and state.
Leo I, Pope, -461--Correpondence.
Princeton subject headings:
Canon law--History.
Church and state--History--Early church, ca. 30-600.
Church history--5th century.
Ecclesiastical law--Rome.
Leo I, Pope, -461.
Leo I, Pope, -461. Correspondence.
Religion and law--Catholic Church.
Religion and law--Rome.