Question: when did the us send advisors to vietnam
[{'answer': 'September 1950', 'provenance': [{'wikipedia_id': '418296', 'title': 'Military Assistance Advisory Group', 'start_paragraph_id': 3, 'start_character': 3, 'end_paragraph_id': 3, 'end_character': 17, 'bleu_score': 1.0, 'section': 'Section::::MAAG Indochina; MAAG Vietnam.\n'}]}, {'provenance': [{'wikipedia_id': '418296', 'title': 'Military Assistance Advisory Group', 'start_paragraph_id': 3, 'start_character': 0, 'end_paragraph_id': 3, 'end_character': 460, 'bleu_score': 0.97451705556073, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 560307668697788833}, 'section': 'Section::::MAAG Indochina; MAAG Vietnam.\n'}]}]