theorem Th33:
  for on being OperName of S, op being OperSymbol of S holds op is
  Element of on iff Name op = on
proof
  let on be OperName of S, op1 be OperSymbol of S;
  hereby
    assume op1 is Element of on;
    then reconsider op = op1 as Element of on;
    (ex op2 being object st op2 in the carrier' of S & on = Class (the
Overloading of S,op2) )& Name op = Class(the Overloading of S,op) by
EQREL_1:def 3;
    hence Name op1 = on by EQREL_1:23;
  end;
  assume Name op1 = on;
  hence thesis by EQREL_1:20;
end;
