Question: when was nanda devi national park added to the unesco's list of world heritage
[{'answer': '1988', 'provenance': [{'wikipedia_id': '4128716', 'title': 'Nanda Devi National Park', 'start_paragraph_id': 3, 'start_character': 67, 'end_paragraph_id': 3, 'end_character': 71, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '4128716', 'title': 'Nanda Devi National Park', 'start_paragraph_id': 3, 'start_character': 0, 'end_paragraph_id': 3, 'end_character': 167, 'bleu_score': 0.934334813046729, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 15671521867509694350}, 'section': 'Section::::Abstract.'}]}]