?url_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.au=Pfiffner%2C+Lukas&rft.aulast=Pfiffner&rft.aufirst=Lukas&rft.date=2001&rft.title=Contributions+of+organic+farming+to+a+sustainable+environment&rft.genre=proceeding