Baumheier, Ralph. 2000. “Co-Operative Planning of Settlements and Open Spaces in the ‘Regio Unterweser’: A New Approach to Cross-Border Co-Operation in the Area Bremen Lower Saxony”. Raumforschung Und Raumordnung | Spatial Research and Planning 58 (4): 337–342. https://doi.org/10.1007/BF03183799.