Question: when did european cup become uefa champions league
[{'answer': '1992', 'provenance': [{'wikipedia_id': '44220', 'title': 'UEFA Champions League', 'start_paragraph_id': 2, 'start_character': 251, 'end_paragraph_id': 2, 'end_character': 255, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]