Question: who sings how long has it been going on
[{'answer': 'George and Ira Gershwin', 'provenance': [{'wikipedia_id': '21146617', 'title': 'How Long Has This Been Going On (disambiguation)', 'start_paragraph_id': 1, 'start_character': 53, 'end_paragraph_id': 1, 'end_character': 76, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'answer': 'Sarah Vaughan', 'provenance': [{'wikipedia_id': '21146617', 'title': 'How Long Has This Been Going On (disambiguation)', 'start_paragraph_id': 3, 'start_character': 48, 'end_paragraph_id': 3, 'end_character': 61, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'answer': 'Van Morrison', 'provenance': [{'wikipedia_id': '21146617', 'title': 'How Long Has This Been Going On (disambiguation)', 'start_paragraph_id': 4, 'start_character': 47, 'end_paragraph_id': 4, 'end_character': 59, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]