Question: when did the denver broncos change their logo
[{'answer': 'February 4 , 1997', 'provenance': [{'wikipedia_id': '8122', 'title': 'Denver Broncos', 'start_paragraph_id': 62, 'start_character': 156, 'end_paragraph_id': 62, 'end_character': 173, 'bleu_score': 1.0, 'section': 'Section::::Logos and uniforms.:1997–2011.\n'}]}, {'provenance': [{'wikipedia_id': '8122', 'title': 'Denver Broncos', 'start_paragraph_id': 62, 'start_character': 0, 'end_paragraph_id': 62, 'end_character': 691, 'bleu_score': 0.9648601406493851, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 13919953321012712025}, 'section': 'Section::::Logos and uniforms.:1997–2011.\n'}]}]