
https://www.cps.org.uk/files/reports/original/201001000814-CPSUPWARDLYMOBILE2.pdf

https://theconversation.com/la-paradoja-de-la-abundancia-como-se-explica-que-un-pais-rico-en-recursos-no-genere-crecimiento-economico-207778

https://ec.europa.eu/commission/publications/terms-reference-article-50-treaty-european-union-negotiations_en