1. International European Agency (IEA). CO2 emissions from fuel combustion highlights; 2014 Edition.
2. Ashby MF. Materials and the Environment. Butterworth Heinemann -Elsevier; 2012.
3. Gutowski T, Sahil S, Allwood J, Ashby M, Worrell E. The energy required to produce materials: constraint on energy intensity-improvements, parameters of demand. Phil Trans R Soc 2013; A 371: 20120003.
4. European Commission, Eurostat. Electricity and natural gas price statistics 2014. Available at http://ec.europa.eu. Accessed on: 27/02/2015.
5. CO2PE! Cooperative effort on process emissions in manufacturing. Available at http://www.co2pe.org. Accessed on: 09/12/2015.