theorem Th36:
  (SpStSeq S)/.2 = NE-corner S
proof
  2 in dom<*NW-corner S,NE-corner S,SE-corner S*> by FINSEQ_1:81;
  hence (SpStSeq S)/.2 = <*NW-corner S,NE-corner S,SE-corner S*>/.2 by
FINSEQ_4:68
    .= NE-corner S by FINSEQ_4:18;
end;
