205.2 Hirsch, Ralph. The Challenge of Urban Planning. Washington, D.C.: American Institute of Planners, 1970. U0.1/No. 20

205.2 Hirsch, Ralph. The Challenge of Urban Planning. Washington, D.C.: American Institute of Planners, 1970. U0.1/No. 20, Box: 28. William J. Cohen papers, MSS 0468. University of Delaware Library Special Collections. https://findingaids.lib.udel.edu/repositories/2/archival_objects/191808 Accessed September 19, 2024.