http://unr.edu/homepage/daved/airqual.html

http://www.aeat.co.uk/netcen/airqual/

http://www.epa.gov

http://www.dbn.csir.co.za/eastcoast/default.htm

http://www.ecoserv.co.za

http://www.skinc.com

http://www.iiasa.ac.com

http://www.pollutiononline.com

http://www.slb.mf.stockholm.se/

http://www.uwe.ac.uk

http://www.environment.detr.gov.uk/airq/aqinfo.htm

http://www.stockholmvatten.se/start/html

http://www.worldbank.org