• Natural Resources Canada 20 April 2009 http://www.oee.nrcan.gc.ca/publications/infosource/pub/home/heating-heat-pump/asheatpumps.cfm
• Swedish Energy Agency 2 April 2009 http://www.energimyndigheten.se/en/Energy-efficiency/Household/Heating-your-home/Heat-pump/Air-source-heat-pump/
• "A heat pump can trim the amount of electricity you use for heating by as much as 30%–40%"
  U.S Department of Energy 24 February 2009  http://www.energysavers.gov/your_home/space_heating_cooling/index.cfm/mytopic=12610
• "Renewables do add up"
  The Guardian 18 September 2008
  http://www.guardian.co.uk/commentisfree/2008/sep/18/energy.energy
• "My plan for Zero Carbon Britain"
  The Guardian 21 August 2008
  http://www.guardian.co.uk/commentisfree/2008/aug/21/greentech.energyefficiency
• "Push for sustainable energy from householders"
  The Telegraph 2 June 2008
  http://www.telegraph.co.uk/earth/earthnews/3343328/Push-for-sustainable-energy-from-householders.html

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