Columbia subject headings:
Harvard subject headings:
Businesspeople--Germany--Hesse-Nassau--Biography.
Family-owned business enterprises--Germany--Hesse-Nassau--History.
Gruen family.
Grün family.
Hesse-Nassau (Germany)--Biography.
Industrialists--Germany--Hesse-Nassau--Biography.
Iron mines and mining--Germany--Hesse-Nassau--History.
Mineral industries--Germany--Hesse-Nassau--History.
Princeton subject headings:
Businesspeople--Germany--Hesse-Nassau--Biography.
Family-owned business enterprises--Germany--Hesse-Nassau--History.
Gruen family.
Iron mines and mining--Germany--Hesse-Nassau--History.
Mineral industries--Germany--Hesse-Nassau--History.