?url_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.au=Koopmans%2C+C.J.&rft.aulast=Koopmans&rft.aufirst=C.J.&rft.date=2007&rft.title=Organic+Soil+Management%3A+Impacts+on+Yields%2C+Soil+Quality+and+Economics&rft.genre=proceeding