https://www.esri.ie/system/files/publications/QEC2022WIN_0.pdf
http://www.ips-journal.eu/topics/european-union/article/show/eu-assurance-co-2037/
https://www.nao.org.uk/wp-content/uploads/2018/01/PFI-and-PF2.pdf
https://www.boeckler.de/fpdf/HBS-008396/p_imk_pb_132_2022.pdf