Hilligardt, Jan. “The Successful Initiation of Voluntary Regional Partnerships in the Implementation of Sustainable Spatial Development”. Raumforschung und Raumordnung | Spatial Research and Planning 61, no. 1-2 (January 31, 2003): 98–106. Accessed May 1, 2024. https://rur.oekom.de/index.php/rur/article/view/1643.