Columbia subject headings:
Harvard subject headings:
Helicopter industry--United States.
Helicopters
Military-industrial complex--United States.
Technology and state--United States.
Tilt rotor aircraft.
United States--Armed Forces--Procurement.
Vertically rising aircraft
Princeton subject headings:
Helicopter industry--United States.
Helicopters.
Tilt rotor aircraft.
United States--Armed Forces--Procurement.