Question: who was the leader of the soviet union in 1967 and 1968
[{'answer': 'Leonid Brezhnev', 'provenance': [{'wikipedia_id': '26865', 'title': 'List of leaders of the Soviet Union', 'start_paragraph_id': 2, 'start_character': 573, 'end_paragraph_id': 2, 'end_character': 588, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]