00321cam a22001097a 4500008004000000082001100040100001600051245006000067260005200127300001000179650002200189180718b1989   xxu||||| |||| 00| 0 eng d  aY Si64  aSingh, H.S.  aPrinciples of environmental conservationcby H.S. Singh  aDehradunbInternational Book Distributorsc1989  a273p.  aNatural resources