Ullman, E. L. (1967). American commodity flow: A geographical interpretation of rail and water traffic ; based on principles of spatial interchange (3. pr.). Univ. of Washington Press.
Chicago-Zitierstil (17. Ausg.)Ullman, Edward L. American Commodity Flow: A Geographical Interpretation of Rail and Water Traffic ; Based on Principles of Spatial Interchange. 3. pr. Seattle u.a: Univ. of Washington Press, 1967.
MLA-Zitierstil (9. Ausg.)Ullman, Edward L. American Commodity Flow: A Geographical Interpretation of Rail and Water Traffic ; Based on Principles of Spatial Interchange. 3. pr. Univ. of Washington Press, 1967.
Achtung: Diese Zitate sind unter Umständen nicht zu 100% korrekt.