With no explanation, label text_A→text_B with either "not_related" or "related".
text_A: Novak Djokovic is from outside Serbia.
text_B: Bear Branch is a stream in the U.S. state of Missouri .. stream. stream. U.S. state. U.S. state. Missouri. Missouri. It is a tributary of Bear Creek .. Bear Branch was named for the bears near its course .
not_related.