Columbia subject headings:
Harvard subject headings:
Helgoland (Germany)--History--20th century.
Helgoland (Germany)--Politics and government--20th century.
National socialism--Germany--Helgoland.
Princeton subject headings:
Helgoland (Germany)--History--20th century.
Helgoland (Germany)--Politics and government--20th century.
National socialism--Germany--Helgoland.