Question: when did they start building the leaning tower of pisa
[{'answer': 'August 14 , 1173'}, {'provenance': [{'wikipedia_id': '46889', 'title': 'Leaning Tower of Pisa', 'start_paragraph_id': 7, 'start_character': 362, 'end_paragraph_id': 7, 'end_character': 654, 'bleu_score': 0.7185585700400201, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 8948116187744588952}, 'section': 'Section::::Construction.\n'}]}]