1. ACEM, 2008. ACEM Yearbook 2007. Facts and Figures on PTWs in Europe. http://www.acembike.org (accessed February 2008).
2. ACI, 2008. ACI, Automobile Club d'Italia. Annuario Statistico 2005. http://www.aci.it/studiericerche/datiestatistiche (assessed 5 February 2008).
3. Particle emissions from a small two stroke engine: effects of fuel, lubricating oil, and exhaust after treatment on particle characteristics;Ålander;Aerosol Science and Technology,2005
4. ANCMA, 2008. ANCMA, Associazione Nazionale Ciclo Motociclo Accessori. http://www.ancma.it (accessed 5 February 2008).
5. Bioavailability in vivo of benzo[a]pyrene adsorbed to diesel particulate;Bevan;Toxicology and Industrial Health,1991