Columbia subject headings:
Harvard subject headings:
Communication and traffic--Germany--Cologne--History.
Communication and traffic--Germany--Rhineland--History.
Transportation--Germany--Cologne--History.
Transportation--Germany--Rhineland--History.
Princeton subject headings:
Communication and traffic--Germany--Cologne--History.
Communication and traffic--Germany--Rhineland--History.
Transportation--Germany--Cologne--History.
Transportation--Germany--Rhineland--History.