Question: who sang the song suddenly with olivia newton john
[{'answer': 'Cliff Richard', 'provenance': [{'wikipedia_id': '25602073', 'title': 'Suddenly (Olivia Newton-John and Cliff Richard song)', 'start_paragraph_id': 0, 'start_character': 33, 'end_paragraph_id': 0, 'end_character': 46, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '25602073', 'title': 'Suddenly (Olivia Newton-John and Cliff Richard song)', 'section': 'Section::::Abstract.', 'start_paragraph_id': 1, 'end_paragraph_id': 1, 'meta': {'evidence_span': ['"Suddenly" is a duet performed by Olivia Newton-John and Cliff Richard from the soundtrack album "Xanadu", and is the love theme from the 1980 film of the same name. It was written and produced by John Farrar.', 'Cliff Richard', 'Suddenly" is a duet performed by Olivia Newton-John and Cliff Richard from the soundtrack album "Xanadu']}}]}]