https://www.whitehouse.gov/wp-content/uploads/2018/10/The-Opportunity-Costs-of-Socialism.pdf
https://czasopisma.uksw.edu.pl/index.php/p/article/download/7285/6507&ved=2ahUKEwjV0c-qnYOAAxWp_7sIHaj9CE8QFnoECAgQAg&usg=AOvVaw0uuJrVk9AhPIMT2xjWvSTQ
https://library.fes.de/pdf-files/iez/19646.pdf
https://www.cidrap.umn.edu/sites/default/files/public/downloads/cidrap-covid19-viewpoint-part1.pdf