Zepp, Harald. “Regional Green Belts in the Ruhr Region. A Planning Concept Revisited in View of Ecosystem Services”. ERDKUNDE 72, no. 1 (March 31, 2018): 1–21. Accessed December 11, 2024. https://journals-test.ulb.uni-bonn.de/index.php/erdkunde/article/view/2823.