With no explanation, label text_A→text_B with either "not_related" or "related".
text_A: Genghis Khan did not practice meritocracy.
text_B: The Men 's Marathon at the 1991 World Championships in Tokyo , Japan was held on September 1 , 1991 .. 1991 World Championships. 1991 World Championships in Athletics. The race started at 18.00 h local time .
not_related.