Columbia subject headings:
World War, 1914-1918--Naval operations--Submarine.
Harvard subject headings:
Merchant ships--History--20th century.
Neutrality.
Ship registers
World War, 1914-1918--Naval operations, German
World War, 1914-1918--Naval operations--Submarine
Princeton subject headings:
World War, 1914-1918--Naval operations--Submarine.