Also I have this thought;
Matt 24:33 So likewise ye, when ye shall see all these things, know that it is near, even at the doors.
Matt 24:34 Verily I say unto you, This generation
shall not pass, till all these things be fulfilled.
If the Jews of 'this generation' are suppose to be the same ones who were audience to Jesus when He spoke this, then they would have more then the sign of Jonas.
Matt 12:39 But he answered and said unto them, An evil and adulterous generation seeketh after a sign; and there shall no sign be given to it, but
the sign of the prophet Jonas: