Columbia subject headings:
Air defenses--Canada--History.
Air defenses--United States--History.
Canada--Military relations--United States.
North American Air Defense Command--History.
United States--Military relations--Canada.
Harvard subject headings:
Air defenses--United States--History.
Canada--Air defenses, Military--History.
Canada--Military relations--United States.
North American Air Defense Command--History.
United States--Military relations--Canada.
Princeton subject headings:
Air defenses--Canada--History.
Air defenses--United States--History.
Canada--Military relations--United States.
North American Air Defense Command--History.
United States--Military relations--Canada.