Birkmann, J.; Finke, L. Indicators for the Evaluation and Guidance of Sustainable Spatial Development in North Rhine-Westphalia: Purposes, Potentials and Problems Associated With the Use of Sustainability Indicators in Area Development Planning in North Rhine-Westphalia. RuR 2001, 59 (4), 276–286. https://doi.org/10.1007/BF03183027.