Columbia subject headings:
Merchant marine--Great Britain.
Shipping--Great Britain.
World War, 1914-1918--Naval operations.
Harvard subject headings:
Merchant marine--Great Britain
Shipping--Great Britain
World War, 1914-1918--Naval operations
Princeton subject headings:
Merchant marine--Great Britain.
Shipping--Great Britain.
World War, 1914-1918--Naval operations.