?url_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.au=Brock%2C+Dipl.geogr.+Christopher&rft.aulast=Brock&rft.aufirst=Christopher&rft.date=2006&rft.title=Balancing+soil+organic+matter+in+organic+agriculture+-+a+theoretical+approach&rft.genre=proceeding