theorem Th67:
  r|= 'X' H iff Shift(r,1)|=H
proof
  r|= 'X' H iff r|= 'X' Evaluate(H,AtomicKai) by Th53;
  then r|= 'X' H iff Shift(r,1)|= Evaluate(H,AtomicKai) by Th59;
  hence thesis;
end;
