Columbia subject headings:
Harvard subject headings:
Catholic Church--History--20th century.
John XXIII, Pope, 1881-1963.
Paul VI, Pope, 1897-1978
Popes--Correspondence
Princeton subject headings:
Catholic Church--History--20th century.
John XXIII, Pope, 1881-1963.
Paul VI, Pope, 1897-1978.
Popes--Correspondence.