http://www.environment.gov.au/atmosphere/airquality/publications/sok/oxides.html

http://epa.gov/climatechange/ghgemissions/gases/n2o.html

http://www.indexmundi.com/facts/singapore/nitrous-oxide-emissions

http://en.wikipedia.org/wiki/Nitrogen_oxide

http://www.belleville.k12.wi.us/bhs/health/environment/nitrogen_oxide.htm

http://www.easychem.com.au/the-acidic-environment/acidic-oxides/sources-of-sulfur-dioxide-and-oxides-of-nitrogen

http://www.elmhurst.edu/~chm/vchembook/193nox.html

http://www.environment.gov.au/atmosphere/airquality/publications/sulfurdioxide.html

http://corrosion-doctors.org/AtmCorros/sulfur-diox.htm

http://en.wikipedia.org/wiki/Air_pollution

http://en.wikipedia.org/wiki/Sulfur_dioxide

http://www.ccohs.ca/oshanswers/chemicals/chem_profiles/sulfurdi/health_sul.html