Question: when was the last time the washington redskins won the superbowl
[{'answer': 'XVIII .', 'provenance': [{'wikipedia_id': '33673', 'title': 'Washington Redskins', 'start_paragraph_id': 28, 'start_character': 1309, 'end_paragraph_id': 28, 'end_character': 1316, 'bleu_score': 1.0, 'section': "Section::::Franchise history.:Joe Gibbs' era (1981–1992).\n"}]}, {'provenance': [{'wikipedia_id': '33673', 'title': 'Washington Redskins', 'start_paragraph_id': 3, 'start_character': 47, 'end_paragraph_id': 3, 'end_character': 751, 'bleu_score': 0.5615701171195581, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 6055970582582347729}, 'section': 'Section::::Abstract.'}]}]