00277nam a2200109 a 450000500170000008200170001710000190003424500340005326000380008730000250012563000170015020251203090734.0  a631.b45 MOR  aMorgan, R.P.C.  aSoil erosion and conservation  aEnglandbLongman Scientificc1986  aix,298p.c24 cm.bPB  aSoil erosion