Columbia subject headings:
Catholic Church--History--20th century.
Papacy--History--20th century.
Popes--Biography.
Harvard subject headings:
Catholic Church--History--20th century.
Papacy--History--20th century
Popes--Biography
Princeton subject headings:
Catholic Church--History--20th century.
Church and state--Catholic Church--History--20th century.
Papacy--History--20th century.
Popes--Biography.