?url_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.au=Kaffka%2C+Stephen&rft.aulast=Kaffka&rft.aufirst=Stephen&rft.date=2005&rft.title=Comparisons+of+organic+and+conventional+maize+and+tomato+cropping+systems+from+a+long-term+experiment+in+California&rft.genre=proceeding