Kubis, Alexander, Matthias Brachert, and Mirko Titze. 2009. “Industrial Clusters As Source of Regional Prosperity? On the Convergence of Germany’s Labour Market Regions 1996–2005”. Raumforschung Und Raumordnung | Spatial Research and Planning 67 (5-6): 341–352. https://doi.org/10.1007/BF03185710.