http://en.wikipedia.org/wiki/List_of_international_call_prefixes#External_links
http://www.itu.int/dms_pub/itu-t/opb/sp/T-SP-E.164C-2011-PDF-E.pdf
http://en.wikipedia.org/wiki/List_of_international_call_prefixes#External_links
http://www.itu.int/dms_pub/itu-t/opb/sp/T-SP-E.164C-2011-PDF-E.pdf