Question: when was the book to kill a mockingbird published
[{'answer': 'on July 11 , 1960', 'provenance': [{'wikipedia_id': '73408', 'title': 'To Kill a Mockingbird', 'start_paragraph_id': 9, 'start_character': 194, 'end_paragraph_id': 9, 'end_character': 211, 'bleu_score': 1.0, 'section': 'Section::::Biographical background and publication.\n'}]}]