Question: who sang the original once upon a dream
[{'answer': 'Mary Costa and Bill Shirley', 'provenance': [{'wikipedia_id': '36967297', 'title': 'Once Upon a Dream (Sleeping Beauty song)', 'start_paragraph_id': 2, 'start_character': 218, 'end_paragraph_id': 2, 'end_character': 245, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]