Breidenbach, Philipp, Rainer Kambeck, Florian Matz, and Christoph M. Schmidt. “Staying Alone or Reaching More Success Together? A Path for More Regional Cooperation in the Ruhrgebiet”. Raumforschung und Raumordnung | Spatial Research and Planning 71, no. 2 (April 30, 2013): 143–156. Accessed March 23, 2025. https://rur.oekom.de/index.php/rur/article/view/736.