Columbia subject headings:
Harvard subject headings:
Airplanes, Military--Germany
Germany. Luftwaffe--History.
Neutrality--Sweden.
World War, 1939-1945--Aerial operations, German.
World War, 1939-1945--Sweden.
Princeton subject headings:
Airplanes, Military--Germany.
Germany. Luftwaffe--History.
Neutrality--Sweden--History--20th century.
World War, 1939-1945--Aerial operations, German.
World War, 1939-1945--Sweden.