↑ "European Union". Encyclopædia Britannica. สืบค้นเมื่อ 1 July 2009. international organisation comprising 27 European countries and governing common economic, social, and security policies....
↑ "European Union". The World Factbook. Central Intelligence Agency. สืบค้นเมื่อ 11 October 2009.
↑ Anneli Albi (2005). "Implications of the European constitution". EU enlargement and the constitutions of Central and Eastern Europe. Cambridge, UK: Cambridge University Press, 2008. p. 204. ISBN90-6704-285-4. สืบค้นเมื่อ 25 July 2011. In practical terms, the EU is perhaps still best characterised as a 'supranational organisation sui generis': this term has proved relatively uncontroversial in respect of national constitutional sensitivities, being at the same time capable of embracing new facets of integration
