Saller, Raymond. “Local-Authority Partnerships Within the Urban Regions of Western Germany: Aspiration and Political Reality”. Raumforschung und Raumordnung | Spatial Research and Planning 58, no. 2-3 (March 31, 2000): 211–221. Accessed July 15, 2024. https://rur.oekom.de/index.php/rur/article/view/1147.