Baumheier, R. . (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