Columbia subject headings:
Harvard subject headings:
Industrialization--Research--Germany--Ruhr (Region)
Learning and scholarship--Germany--Ruhr (Region)
Research--Germany--Ruhr (Region)
Princeton subject headings:
Research--Germany--Ruhr (Region)--History.
Science and industry--Germany--Ruhr (Region)--History.
Science--Germany--Ruhr (Region)--History.
Social sciences--Germany--Ruhr (Region)--History.