Question: who were the backup singers for elvis presley
[{'answer': 'The Jordanaires', 'provenance': [{'wikipedia_id': '1775193', 'title': 'The Jordanaires', 'start_paragraph_id': 0, 'start_character': 0, 'end_paragraph_id': 0, 'end_character': 15, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '1775193', 'title': 'The Jordanaires', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 334, 'bleu_score': 0.965203995518735, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 3039238283881887364}, 'section': 'Section::::Abstract.'}]}]