theorem Th2:
  Stop SCM+FSA does not refer aa
proof
A1: rng Stop SCM+FSA = {halt SCM+FSA} by AFINSQ_1:33;
  let i be Instruction of SCM+FSA;
  assume i in rng Stop SCM+FSA;
  then i = halt SCM+FSA by A1,TARSKI:def 1;
  hence thesis;
end;
