Columbia subject headings:
Communication--Economic aspects--History--Congresses.
Communication--Social aspects--History--Congresses.
Pohl, Hans.
Harvard subject headings:
Communication and traffic--History--Congresses.
Communication--Economic aspects--History--Congresses.
Communication--History--Congresses.
Communication--Social aspects--History--Congresses.
Pohl, Hans.
Princeton subject headings:
Communication--History--Congresses.
Communication--Social aspects--Congresses.