Columbia subject headings:
Harvard subject headings:
Great Britain. Royal Navy--History--World War, 1939-1945.
Merchant marine--Great Britain--History--20th century.
World War, 1939-1945--Naval operations, British.
Princeton subject headings:
Great Britain. Royal Navy--History--World War, 1939-1945.
Merchant marine--Great Britain--History--20th century.
World War, 1939-1945--Naval operations, British.