https://www.osw.waw.pl/sites/default/files/pw_69_pesco_ang_net.pdf
https://larouchepub.com/eiw/public/2014/eirv41n08-20140221/34-35_4108.pdf
https://giwps.georgetown.edu/wp-content/uploads/2019/12/WPS-Index-2019-20-Report.pdf
https://www.osce.org/library/14127?download=true