@unpublished{bringezu1996the,
  title = {The ecological backpack of the Ruhr area: a comparison with North Rhine-Westphalia and the Federal Republic of Germany}
  author = {Bringezu, Stefan; Schütz, Helmut},
  publisher = {Factor X: Challenges, Implementation Strategies and Examples for a Sustainable Use of Natural Resources},
  url = {https://epub.wupperinst.org/frontdoor/index/index/docId/428},
  year = {1996}
}