Wolf, Klaus. “Qualifications for Spatial Planning: Ideas from the Diploma Course in Geography at the J. W. Goethe University of Frankfurt Am Main”. Raumforschung Und Raumordnung | Spatial Research and Planning, vol. 57, no. 5-6, Sept. 1999, pp. 371–374, https://doi.org/10.1007/BF03184504.