?url_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.isbn=9290664770&rft.date=2005&rft.btitle=Sustainable+Agriculture+Systems+for+the+Drylands.+Proceedings+of+the+International+Symposium+for+Sustainable+Dryland+Agriculture+Systems%2C+2%E2%80%935+December+2003%2C+Niamey%2C+Niger&rft.genre=book