Question: when was crude oil first discovered in nigeria
[{'answer': '15 January 1956', 'provenance': [{'wikipedia_id': '27436052', 'title': 'Oloibiri Oilfield', 'start_paragraph_id': 4, 'start_character': 43, 'end_paragraph_id': 4, 'end_character': 58, 'bleu_score': 1.0, 'section': 'Section::::Exploration history.\n'}]}, {'provenance': [{'wikipedia_id': '27436052', 'title': 'Oloibiri Oilfield', 'start_paragraph_id': 4, 'start_character': 0, 'end_paragraph_id': 4, 'end_character': 303, 'bleu_score': 0.958740481558872, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 10318804126336284061}, 'section': 'Section::::Exploration history.\n'}]}]