1. BP Statistical Review of World Energy,2013
2. EEA Report – No 6/2008, Energy and Environment Report 2008,2008
3. U.S. Energy Information Administration (EIA), http://www.eia.gov/cfapps/ipdbproject/IEDIndex3.cfm?tid=44&pid=44&aid=2 (retrieved on 18/04/2014).
4. Directive 2004/8/EC of the European Parliament and of the Council of the 11 February 2004 on the promotion of cogeneration based on the useful heat demand in the internal energy market and amending Directive 92/42/EEC;Off. J. Eur. Union,2004