With no explanation, label text_A→text_B with either "not_related" or "related".
text_A: Boris Karloff was an English actor.
text_B: In mathematics , the Mestre bound is a bound on the analytic rank of an elliptic curve in terms of its conductor , introduced by .. mathematics. mathematics. analytic rank. analytic rank. elliptic curve. elliptic curve
not_related.