Columbia subject headings:
Harvard subject headings:
Communication--Germany--Ruhr (Region)--History--18th century.
Mass media--Social aspects--Germany--Ruhr (Region)--History--18th century.
Press--Germany--Ruhr (Region)--History--18th century.
Princeton subject headings:
Communication--Germany--Ruhr (Region)--History--18th century.
Mass media--Social aspects--Germany--Ruhr (Region)--History--18th century.
Press--Germany--Ruhr (Region)--History--18th century.