http://home.howstuffworks.com/question181.htm 
http://www.onlinegardenertips.com/Fertilizer/How-Does-Fertilizer-Work.html 
http://www.basicsofgardening.com/5-types-of-fertilizer.html 
http://www.ehow.com/how-does_4564047_fertilizer-work.html
http://www.tropicalpermaculture.com/what-is-fertilizer.html


http://www.ncagr.gov/cyber/kidswrld/plant/label.htm

http://www.doityourself.com/stry/harvest-incredible-romaine-lettuce-with-organic-fertilizer#b

http://www.smilinggardener.com/organic-fertilizers/10-10-10-fertilizer


http://www.fertilizer.org 

http://www.bigoven.com/organic-vs-inorganic-foods

http://www.turfprousa.com/health_effects_of_synthetic_fertilizer_3006a.html

http://www.sustainablebabysteps.com/effects-of-chemical-fertilizers.html

http://environment.nationalgeographic.co.uk/environment/green-guide/buying-guides/fertilizer/environmental-impact/

http://www.davidpublishing.com/davidpublishing/Upfile/3/23/2012/2012032310127195.pdf

     
https://www.agronomy.org/publications/aj/abstracts/97/1/0001?access=0&view=article