United States. Office of Aviation Economics. (1972). Air passenger trip travel times: ground and air: 1968 and 1972. [Washington]: Dept. of Transportation, Federal Aviation Administration, Office of Aviation Economics.
Petikan Gaya ChicagoUnited States. Office of Aviation Economics. Air Passenger Trip Travel Times: Ground and Air: 1968 and 1972. [Washington]: Dept. of Transportation, Federal Aviation Administration, Office of Aviation Economics, 1972.
Petikan MLAUnited States. Office of Aviation Economics. Air Passenger Trip Travel Times: Ground and Air: 1968 and 1972. [Washington]: Dept. of Transportation, Federal Aviation Administration, Office of Aviation Economics, 1972.
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