Question: when did the battle of britain begin and end
[{'answer': '10 July', 'provenance': [{'wikipedia_id': '57974', 'title': 'Battle of Britain', 'start_paragraph_id': 1, 'start_character': 413, 'end_paragraph_id': 1, 'end_character': 420, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'answer': '31 October 1940', 'provenance': [{'wikipedia_id': '57974', 'title': 'Battle of Britain', 'start_paragraph_id': 1, 'start_character': 427, 'end_paragraph_id': 1, 'end_character': 442, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]