00447cam a22000977a 4500008004000000082001400040245021600054260003500270300000900305700003500314180718b1970   xxu||||| |||| 00| 0 eng d  aI5517 Un3  aSymposium on the application of operational research methods in solving the economic problems of planning and operating large electric power systems and on the use of computerscby Economic Commission for Europe  aNew YorkbUnited Nationsc1970  av.p.  aEconomic Commission for Europe