1. European Environment Agency (EEA). Greenhouse gas emission trends and projections in Europe 2008, Annex: additional information on greenhouse gas emission trends and projections by sector and by Member State, Report No. 5/2008.
2. European Commission. Directive 2003/30/EC of the European Parliament and the Council on the promotion of the use of biofuels or other renewable fuels for transport. Off J Euro Union [17.5.2003].
3. European Commission. Green paper: towards a European strategy for the security of energy supply. Luxembourg; 2001. 105 p. ISBN: 92-894-0319-5. .
4. European Commission. White paper: European transport policy for 2010: time to decide. Luxembourg; 2001. 119 p. ISBN: 92-894-0341-1. .
5. Natural gas as an alternative to crude oil in automotive fuel chains wee-to-wheel analysis and transition strategy development;Hekkert;Energy Policy,2005