Question: when did the battle of britain ww2 start
[{'answer': 'July 1940', 'provenance': [{'wikipedia_id': '57974', 'title': 'Battle of Britain', 'start_paragraph_id': 2, 'start_character': 105, 'end_paragraph_id': 2, 'end_character': 114, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '57974', 'title': 'Battle of Britain', 'start_paragraph_id': 1, 'start_character': 237, 'end_paragraph_id': 1, 'end_character': 567, 'bleu_score': 0.601793695710209, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 6482531367222449734}, 'section': 'Section::::Abstract.'}]}]