Question: when did the soviet union take over poland
[{'answer': '17 September 1939', 'provenance': [{'wikipedia_id': '7884711', 'title': 'Soviet invasion of Poland', 'start_paragraph_id': 1, 'start_character': 115, 'end_paragraph_id': 1, 'end_character': 132, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '7884711', 'title': 'Soviet invasion of Poland', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 591, 'bleu_score': 0.909891904163391, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 1306061343125202826}, 'section': 'Section::::Abstract.'}]}]