1. Müller-Langer F (2009) Biomethane options for mobile use. 7th international colloquium fuels mineral oil based and alternative fuels, German Biomass Research Centre, Technische Akademie Esslingen
2. Directive on the promotion of the use of biofuels or other renewable fuels for transport (2003) European Parliament and Council’s directive 2003/30/EC, status: May 2003
3. Renewable energy directive (2008) European Parliament and Council’s directive proposal 2008/0016 (COD), status: December 2008
4. Regulation on type approval of motor vehicles with respect to emissions from light passenger and commercial vehicles (EURO 5 and EURO 6) (2007) European Parliament and Council’s regulation (EC) No. 715/2007, status: June 2007
5. Federal and California exhaust and evaporative emission standards for light-duty vehicles and light-duty trucks (2008) Environmental Protection Agency EPA420-B-00-001, status: February 2008