reserve UA for Universal_Algebra,
  f, g for Function of UA, UA;
reserve I for set,
  A, B, C for ManySortedSet of I;
reserve S for non void non empty ManySortedSign,
  U1, U2 for non-empty MSAlgebra over S;

theorem Th25:
  for f be Element of MSAAut U1 holds f"" in MSAAut U1
proof
  let f be Element of MSAAut U1;
  f is_isomorphism U1, U1 by Def5;
  then f"" is_isomorphism U1, U1 by MSUALG_3:14;
  hence thesis by Def5;
end;
