The World Factbook. (2006). Washington: Central Intelligence Agency. Retrieved 8 August 2006 from Appendix GArxivat 2011-04-06 a Wayback Machine..(anglès)
The World Factbook. (2006). Washington: Central Intelligence Agency. Retrieved 8 August 2006 from Appendix GArxivat 2011-04-06 a Wayback Machine..(anglès)