1. Lygnerud, K. Value creating innovations in the pipeline – a case study on residential house district heating investments in Sweden. Licentiate thesis, Gothenburg University, Sweden; 2006.
2. Statens Energimyndighet (Swedish Energy Agency). ER 2006:31; 2006.
3. Statistics Finland; 2006 and 2007. Information collected at website: .
4. Statens Energimyndighet och SCB (Swedish Energy Agency and Statistics Sweden). EN 16 SM 0704; 2008.
5. Euroheat. District heating system ownership guide; 2008. .