Columbia subject headings:
Ecology--Europe--History.
Ecology--History.
Land use--Europe--Planning.
Harvard subject headings:
Economic development--Environmental aspects--Germany (East)--History--Congresses.
Industries--Germany (East)--History--Congresses.
Land use--Germany (East)--History--Congresses.
Princeton subject headings:
Ecology--Europe--History.
Ecology--History.
Land use--Europe--Planning.