Columbia subject headings:
Harvard subject headings:
Environmental policy--Germany (East)--History--20th century.
Environmental policy--Germany--History--20th century.
Environmental protection--Germany (East)--History--20th century.
Environmental protection--Germany--History--20th century.
Nature conservation--Germany (East)--History--20th century.
Nature conservation--Germany--History--20th century.
Princeton subject headings:
Environmental policy--Germany (East)--History--20th century.
Environmental policy--Germany--History--20th century.
Environmental protection--Germany (East)--History--20th century.
Environmental protection--Germany--History--20th century.
Nature conservation--Germany (East)--History--20th century.
Nature conservation--Germany--History--20th century.