Columbia subject headings:
Harvard subject headings:
Submarine warfare--Germany--History--20th century.
Submarines (Ships)--Germany--History--20th century
World War, 1914-1918--Naval operations, German
World War, 1914-1918--Naval operations--Submarine
World War, 1914-1918--Personal narratives, German
Princeton subject headings:
Submarine warfare--Germany--History--20th century.
Submarines (Ships)--Germany--History--20th century.
World War, 1914-1918--Naval operations, German.
World War, 1914-1918--Naval operations--Submarine.
World War, 1914-1918--Personal narratives, German.