Question: when did the dallas cowboys come into the nfl
[{'answer': 'March 19 , 1960', 'provenance': [{'wikipedia_id': '9974238', 'title': 'History of the Dallas Cowboys', 'start_paragraph_id': 6, 'start_character': 75, 'end_paragraph_id': 6, 'end_character': 90, 'bleu_score': 1.0, 'section': 'Section::::1960s.:Origins.\n'}]}, {'provenance': [{'wikipedia_id': '9974238', 'title': 'History of the Dallas Cowboys', 'start_paragraph_id': 6, 'start_character': 0, 'end_paragraph_id': 6, 'end_character': 589, 'bleu_score': 0.9203951459836621, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 2163845790116227266}, 'section': 'Section::::1960s.:Origins.\n'}]}]