Columbia subject headings:
Harvard subject headings:
Labor leaders--Germany--Biography.
Labor unions and fascism--Germany.
Nazi concentration camp inmates--Germany--Correspondence
Oranienburg (Concentration camp)
Sachsenhausen (Concentration camp)
Princeton subject headings:
Labor unions--Officials and employees--Biography.
Oranienburg (Concentration camp)--Biography.
Political prisoners--Germany--Biography.
Sachsenhausen (Concentration camp)--Biography.