00355nam a2200121Ia 450000500170000000800410001702000150005805000260007310000170009924500680011626000330018465000160021720251229184544.0251229s9999    xx            000 0 und d  a0121598500  aS 494.5 .P75B56 C.1-7  aCarlson, P.S 4aThe biology of crop productivity/ ed by P.S. CarlsoncP Carlson  aNew YorkbAcademic Pr.c1980  aCrop Yields