00286nam a2200109Ia 4500082002200000100001600022245006700038260004800105300001300153500000500166700000500171  a338.1091bG857.AS  aGrigg, D. B  aAgricultural systems of the world; and evolutionary approachb  aCambridgebCambridge University Pressc1974  ax, 358p.  a  a