Columbia subject headings:
Catholic Church--Relations--Protestant churches.
Christian union--Catholic Church.
Church--Unity.
Rahner, Karl, 1904-1984.
Theology, Doctrinal--History.
Harvard subject headings:
Christian union.
Fries, Heinrich. Einigung der Kirchen--reale Möglichkeit.
Rahner, Karl, 1904-1984.
Princeton subject headings: