Columbia subject headings:
Harvard subject headings:
Naval art and science--Germany--History--20th century.
Shipbuilding--Germany--History--20th century.
Submarines (Ships)--Germany--Design and construction.
Submarines (Ships)--Germany--History--20th century
Princeton subject headings:
Naval art and science--Germany--History--20th century.
Shipbuilding--Germany--History--20th century.
Submarines (Ships)--Germany--Design and construction.
Submarines (Ships)--Germany--History--20th century.