Question: when was the last pow released from vietnam
[{'answer': '1973', 'provenance': [{'wikipedia_id': '4603167', 'title': 'Robert R. Garwood', 'start_paragraph_id': 2, 'start_character': 143, 'end_paragraph_id': 2, 'end_character': 147, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '4603167', 'title': 'Robert R. Garwood', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 193, 'bleu_score': 0.6362638117929541, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 9646795121330852047}, 'section': 'Section::::Abstract.'}]}]