Helvig, M. (1964). Chicago's external truck movements: Spatial interactions between the Chicago area and its hinterland. Chicago: University of Chicago.
Παραπομπή Chicago StyleHelvig, Magne. Chicago's External Truck Movements: Spatial Interactions between the Chicago Area and Its Hinterland. Chicago: University of Chicago, 1964.
Παραπομπή MLAHelvig, Magne. Chicago's External Truck Movements: Spatial Interactions between the Chicago Area and Its Hinterland. Chicago: University of Chicago, 1964.
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