00403nam a2200145Ia 4500008004100000020001500041082001700056100001600073245004500089260005200134300000800186650001400194650002000208653002900228170901s1989    xx            000 0 und d  a8770891019  a333.72bS48P  aSingh, H.S. 0aPrinciples of Environmental Conservation  aDehradunbInternational Book Distributorsc1989  a273  aEconomics  aSocial sciences  aEnvironmental protection