Question: when was at&t stadium built in san francisco
[{'answer': 'December 11 , 1997', 'provenance': [{'wikipedia_id': '361262', 'title': 'Oracle Park', 'start_paragraph_id': 7, 'start_character': 40, 'end_paragraph_id': 7, 'end_character': 58, 'bleu_score': 1.0, 'section': 'Section::::History.:Design and construction.\n'}]}]