1. Air Quality in Europe— 2011, Report. European Environment Agency. ISBN:978–92–9213–232–3,http://www.eea.europa.eu/.
2. Regulation (EC) No. 715/2007 of the European Parliament and of the Council of 20 June 2007, on type approval of motor vehicles with respect to emissions from light passenger and commercial vehicles (Euro 5 and Euro 6) and on access to vehicle repair and maintenance information,http://eur-lex.europa.eu/en/index.htm.
3. Directive 2008/50/EC of the European Parliament and of the Council of 21 May 2008, on ambient air quality and cleaner air for Europe,http://eur-lex.europa.eu/en/index.htm.
4. The Motor Vehicles (EC Type Approval) (Amendment) Regulations 2008, (No. 2844), United Kingdom,www.legislation.gov.uk.
5. The Air Quality Standards Regulations 2010, (No. 1001), United Kingdom,www.legislation.gov.uk.