Question: when did the cold war officially start and end
[{'answer': '1947', 'provenance': [{'wikipedia_id': '325329', 'title': 'Cold War', 'start_paragraph_id': 1, 'start_character': 397, 'end_paragraph_id': 1, 'end_character': 401, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'answer': 'and either 1989 , when communism fell in Eastern Europe , or 1991 , when the Soviet Union collapsed'}]