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2. Chicago’s External Truck Movements; Spatial Interactions Between the Chicago Area and Its Hinterland;Helvig,1964
3. Forecasting Urban Travel: Past, Present and Future;Boyce,2015
4. Methods for the Study of Retail Relationships;Reilly,1929
5. Intervening opportunities: A theory relating mobility and distance;Stouffer;Amer. Sociol. Rev.,1940