
https://www.ips-journal.eu/topics/economy-and-ecology/its-the-real-economy-stupid-7603/

https://papers.ssrn.com/sol3/Delivery.cfm/SSRN_ID3950757_code410506.pdf?abstractid=3909166&mirid=1

http://www.cbi.org.uk/index.cfm/_api/render/file/?method=inline&fileID=7C026F7C-746E-4795-90EFCC69B2FB6756