1. Directive 2012/27/EU on energy efficiency.
2. European Commission. Energy Efficiency Plan 2011, 8 March 2011.
3. Directive 2009/28/EC on the promotion of the use of energy from renewable sources.
4. International Energy Agency. Technology Roadmap. Energy-efficient buildings: heating and cooling equipment, 2011.
5. Nowak T. European Heat Pump Association predicts market recovery in 2012. Market reports. REHVA Journal, October 2012.