Ullman, E. L. (1957). American commodity flow: A geographical interpretation of rail and water traffic based on principles of spatial interchange. Univ. of Washington Press.
Chicago-Zitierstil (17. Ausg.)Ullman, Edward Louis. American Commodity Flow: A Geographical Interpretation of Rail and Water Traffic Based on Principles of Spatial Interchange. Seattle: Univ. of Washington Press, 1957.
MLA-Zitierstil (9. Ausg.)Ullman, Edward Louis. American Commodity Flow: A Geographical Interpretation of Rail and Water Traffic Based on Principles of Spatial Interchange. Univ. of Washington Press, 1957.
Achtung: Diese Zitate sind unter Umständen nicht zu 100% korrekt.