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

http://www.ec.gc.ca/acidrain/acidfact.html

http://www.ypte.org.uk/docs/factsheets/env_facts/acid_rain.html

http://library.thinkquest.org/CR0215471/acid_rain.htm

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/A/AcidRain.html