Columbia subject headings:
Harvard subject headings:
Baltic Sea Region--History.
Poland--History--Occupation, 1939-1945
World War, 1939-1945--Campaigns--Baltic Sea Region.
World War, 1939-1945--Campaigns--Poland.
World War, 1939-1945--Naval operations, German.
World War, 1939-1945--Naval operations, Polish.
Princeton subject headings:
World War, 1939-1945--Baltic Sea.
World War, 1939-1945--Naval operations, Polish.