00307nam a2200109Ia 4500082001800000100001700018245008800035300001600123490001800139490003500157500000500192  a382.72 L533b  aLeith, J. C.  aSubstitution and supply elasticities in calculating the effective protective rateb  app. 588-601  vNovember 1968  aQuarterly Journal of Economics  a