1) Harrington, W., McConnell, V. and Ando, A.: Are vehicle emission inspection programs living up to expectations? Transportation Research D, Vol. 5D, pp. 153-172, 2000.
2) Vehicle Inspectorate Agency, Department of Environment, Transport and the Regions, UK: http://www.via.gov.uk
3) Union Technique de l'Automobile, du Motocyde et du Cycle: http://www.utac.com