«2011 FedEx Rate Changes», FedEx.com, FedEx, January 3, 2011, http://www.fedex.com/us/2011rates/ratechanges.html и «Postal Service Adjusts Mailing Services Prices for 2012», United States Postal Service press release, October 18, 2011, на сайте USPS, http://about.usps.com/news/national-releases/2011/pr11_116.htm.