1. 1) Department of the Environment (1993) Ozone in the United Kingdom 1993, Third Report of the United Kingdom Photochemical Oxidants Review Group, DOE, London.
2. 2) US Environmental Protection Agency (2007) Control of Hazardous Air Pollutants from Mobile Sources. EPA420-R-07-002, Assessment and Standards Division, Office of Transportation and Air Quality, U.S. EPA, February 2007.
3. Ambient air levels of volatile organic compounds in Latin American and Asian cities
4. 4) Philippine Department of Transportation, Land Transportation Office. Summary of the Number of Motor Vehicles Registered, For Hire, By Type of Service, Metro Manila, CY 1990-CY 2006. http://www.lto.gov.ph/stats2006/SUMMARYOFTHENUMBEROFMOTORVEHICLESREGISTEREDFORHIREBYTYPEOFSERVICE_MM90_06.pdf. Accessed on January 16, 2008.
5. Public Bus and Taxicab Drivers' Work-Time Exposure to Aromatic Volatile Organic Compounds