Question: america's involvement in the vietnam war ended under the administration of president
[{'answer': 'Nixon', 'provenance': [{'wikipedia_id': '8453309', 'title': 'Role of the United States in the Vietnam War', 'start_paragraph_id': 119, 'start_character': 8, 'end_paragraph_id': 119, 'end_character': 13, 'bleu_score': 1.0, 'section': 'Section::::Vietnamization, 1969–73.\n'}]}, {'provenance': [{'wikipedia_id': '8453309', 'title': 'Role of the United States in the Vietnam War', 'start_paragraph_id': 147, 'start_character': 0, 'end_paragraph_id': 147, 'end_character': 363, 'bleu_score': 0.9657992495762461, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 12197106197300891790}, 'section': 'Section::::Vietnamization, 1969–73.:Return to Paris.\n'}]}]