displays to guide a landing airplane to the runway by transmitting verbal commands to the pilot. The system was simple, direct, and worked well, even with previously untrained pilots. It was so successful that the military continued to use it for many years after the war, and it was still in use in some countries in the 1980s. With population growth, new indigenous quarters were created. The Alliance of Democratic Forces for the Liberation of Congo rebels captured Lubumbashi in April 1997. The high altitude serves to cool the climate, which would otherwise be very hot. Failing health reduced Hitchcock's output during the last two decades of his life. Hitchcock's films sometimes feature characters struggling in their relationships with their mothers. Hitchcock preferred to work with the best