00290nam a2200109Ia 450000500170000000800410001708200120005810000200007024500400009026000410013030000090017120260225050922.0260224s9999||||xx |||||||||||||| ||und||  a633 MAR  aJohn H. Martin  0aPrinciples of field crop poduction   aIslamabad: National Book Foundation   a1044