With no explanation, label text_A→text_B with either "not_related" or "related".
text_A: Leonardo da Vinci studied earth science.
text_B: Proud Clarion -LRB- January 19 , 1964 -- December 17 , 1981 -RRB- was an American Thoroughbred racehorse best known for winning the 1967 Kentucky Derby .. Kentucky Derby. Kentucky Derby. American. United States. Thoroughbred. Thoroughbred. racehorse. horse racing
not_related.