Columbia subject headings:
Catholic Church--Relations--Protestant churches.
Protestant churches--Relations--Catholic Church.
Tillich, Paul, 1886-1965.
Harvard subject headings:
Catholic Church--Relations--Protestant churches.
Protestant churches--Relations--Catholic Church
Tillich, Paul, 1886-1965
Princeton subject headings:
Catholic Church--Relations--Protestant churches.
Protestant churches--Relations--Catholic Church.
Tillich, Paul, 1886-1965.