00279nam a2200109Ia 450000500170000000800410001708200120005810000190007024500330008926000390012230000080016120260224040900.0260224s9999||||xx |||||||||||||| ||und||  a630 DUC  aDuckham, A.N.  0aFarming systems of the world  aNew York: Praeger Publishersc1970  a542