Question: when did the philosopher's stone come out
[{'answer': '26 June 1997', 'provenance': [{'wikipedia_id': '48648', 'title': "Harry Potter and the Philosopher's Stone", 'start_paragraph_id': 2, 'start_character': 54, 'end_paragraph_id': 2, 'end_character': 66, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]