[1] ANACOM (2008), Study ''Comparisons of prices of the universal postal service providers in the European Union'', available at: Study 'Comparisons of prices of providers of the universal postal service in the European Union'https://www.anacom.pt/render.jsp?contentId=737718.
[2] ANACOM (2009), “Comparisons of prices of the Universal Postal Service providers in the European Union” in 2009”, available at: Study ''Comparisons of prices of universal postal service providers in the European Union in 2009''https://www.anacom.pt/render.jsp?contentId=997559.
[3] ANACOM (2011), Study “Comparisons of prices of the Universal Postal Service providers in the European Union in 2010” available at: Study ''Comparisons of prices of Universal Postal Service providers in the European Union in 2010'' - Summaryhttps://www.anacom.pt/render.jsp?contentId=1066054.
[4] ANACOM (2011b), “Challenges faced by the postal sector in light of full liberalisation”.
[5] ANACOM (2012), Study “Comparisons of prices of the Universal Postal Service providers in the European Union in 2011” available at: Comparison of pricing - providers of Universal Postal Service in the European Union (2011)https://www.anacom.pt/render.jsp?contentId=1115599.
[6] Deutsche Post (2015), “Letter Prices in Europe”.
[7] EGIDE and IMR (2015) “Development of the Postal Sector in Portugal”, study carried out for ANACOM.
[8] ERGP (2013), “ERGP (12) 33 - ERGP Report with data on indicators on the postal market”.
[9] ERGP (2014), “ERGP(13) 33 Rev. 1 - ERGP Report on indicators on the postal market”.
[10] NERA Economic Consulting (2004), “Economics of Postal Services”, study carried out for the European Commission.
[11] Schreyer, P. And F. Koechlin (2002), “Purchasing Power Parities - measurement and uses “Statistics Brief, March no. 3, OECD.
[12] WIK-Consult (2013), "Main Developments in the Postal Sector (2010-2013)", study carried out for the European Commission.
