Columbia subject headings:
Apologetics--History--20th century.
Christian union.
Creeds.
Ecumenical movement.
Theology--History--20th century.
World Council of Churches. Commission on Faith and Order.
Harvard subject headings:
Apologetics.
Christian union.
Creeds.
Ecumenical movement.
Theology.
World Council of Churches. Commission on Faith and Order.
Princeton subject headings: