Question: when did stephen hawking wrote a brief history of time
[{'answer': '1988', 'provenance': [{'wikipedia_id': '67227', 'title': 'A Brief History of Time', 'start_paragraph_id': 1, 'start_character': 189, 'end_paragraph_id': 1, 'end_character': 193, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '67227', 'title': 'A Brief History of Time', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 291, 'bleu_score': 0.908198718008664, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 11249009795314758763}, 'section': 'Section::::Abstract.'}]}]