?url_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.au=Litterick%2C+Audrey+M&rft.aulast=Litterick&rft.aufirst=Audrey+M&rft.date=2002&rft.title=An+investigation+into+the+relationship+between+preceding+break+crops+and+weed+populations+in+barley+crops+in+organic+ley%2Farable+rotations+&rft.genre=proceeding