Question: when did the nuclear non proliferation treaty start
[{'answer': '1970', 'provenance': [{'wikipedia_id': '22107', 'title': 'Treaty on the Non-Proliferation of Nuclear Weapons', 'start_paragraph_id': 2, 'start_character': 63, 'end_paragraph_id': 2, 'end_character': 67, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '22107', 'title': 'Treaty on the Non-Proliferation of Nuclear Weapons', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 762, 'bleu_score': 0.949685363589651, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 15618262450150015445}, 'section': 'Section::::Abstract.'}]}]