Columbia subject headings:
Catholic Church--Relations.
Christian union--Catholic Church.
Ecumenical movement--History.
World Council of Churches.
Harvard subject headings:
Catholic Church--Relations--Eastern churches.
Catholic Church--Relations--Protestant churches.
Catholic Church--Relations.
Christian union--Catholic Church
Eastern churches--Relations--Catholic Church
Ecumenical movement--History--20th century.
Ecumenical movement.
Protestant churches--Relations--Catholic Church
World Council of Churches
World Council of Churches--History.
Princeton subject headings: