?url_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.au=Lien%2C+Dr.+Gudbrand&rft.aulast=Lien&rft.aufirst=Gudbrand&rft.date=2006&rft.title=Risk+and+economic+sustainability+of+crop+farming+systems+&rft.genre=proceeding