Columbia subject headings:
Harvard subject headings:
Industrialists--Germany--Mülheim an der Ruhr--Biography.
Theis family--Correspondence.
Thyssen, August, 1842-1926--Correspondence.
Thyssen-Bornemisza, Heinrich, Baron--Correspondence.
Princeton subject headings:
Industrialists--Germany--Mülheim an der Ruhr--Biography.
Theis family--Correspondence.
Thyssen, August, 1842-1926--Correspondence.
Thyssen-Bornemisza, Heinrich, Baron--Correspondence.