Question: who was the last team to win the world series back to back
[{'answer': 'New York Yankees', 'provenance': [{'wikipedia_id': '7599168', 'title': 'List of World Series champions', 'start_paragraph_id': 3, 'start_character': 111, 'end_paragraph_id': 3, 'end_character': 127, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]