Question: when did the second sino japanese war start
[{'answer': 'July 7 , 1937', 'provenance': [{'wikipedia_id': '69980', 'title': 'Second Sino-Japanese War', 'start_paragraph_id': 154, 'start_character': 63, 'end_paragraph_id': 154, 'end_character': 76, 'bleu_score': 1.0, 'section': 'Section::::Casualties.\n'}]}, {'provenance': [{'wikipedia_id': '69980', 'title': 'Second Sino-Japanese War', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 296, 'bleu_score': 0.96188712955549, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 15631351798676880780}, 'section': 'Section::::Abstract.'}]}]