  Carefully analyze influence of the tortoise coordinates r* and t on the
stable study of the Schwarzschild black hole. Actually, one should be cautious
in using the compact property of the perturbation field: it is true only with
respect with the coordinate r and proper time or "good time", not the tortoise
coordinates r* and t. Therefore, the mathematical proof used in reference [7]
is incorrect because of it relying on the compact property of the perturbation
fields. The Schwarzschild black hole might be unstable[1]-[5]
