Delaware Health And Social Services http://dhss.delaware.gov/dph/files/ammoniapi.pdf accessed May 2007.
Tennessee Department of Health http://health.state.tn.us/environmental/ammonia.shtml
Health Protection Agency http://www.hpa.org.uk/webc/HPAwebFile/HPAweb_C/1194947398613 accessed 2007
Colorado state - Ammonia Best Management Practices For livestock operations http://ammoniabmp.colostate.edu/link%20pages/what%20is%20ammonia.html accessed 20 June 2008
Ammonia (<--name of page) http://www.ch.ic.ac.uk/rzepa/mim/environmental/html/ammonia_text.htm
Chemguide - The Haber Process http://www.chemguide.co.uk/physical/equilibria/haber.html accessed April 2013
Encyclopedia Britannica http://www.britannica.com/EBchecked/topic/20940/ammonia-NH3
(some webpages did not display the last or exact time they were accessed and didn't display their author