Originally posted by: syria2014
http://www.ces.purdue.edu/extmedia/ID/ID-346-W.pdfhttp://www.card.iastate.edu/iowa_ag_review/winter_08/article3.aspxIf ur doing a paper these websites are reliable!r u doing a paper by any chance? U should try to research more on EPA website.! Hope this helps, let me know if this just a question for your test or exam or ur doing a paper.!😳