https://www.globalwitness.org/en/campaigns/oil-gas-and-mining/pipe-down/
https://www.dbresearch.de/PROD/RPS_DE-PROD/PROD0000000000523908/Deutschland%3A_Konjunktur_kurzgefasst.PDF
https://www.nscai.gov/wp-content/uploads/2021/03/Full-Report-Digital-1.pdf
http://www.debtwire.com/pdf/EuropeanNPLFY18!.pdf