00294nam a2200097Ia 450000500170000000800410001705000160005810000220007424500650009626000350016120251229191223.0251229s9999    xx            000 0 und d  aS 540  .E36  aEvenson, Robert E 0aAgricultural Research and the productivitycRobert E Evenson  aLondonb  Yale uni pressc1975