Question: when did the us sign the treaty of versailles
[{'answer': '28 June 1919', 'provenance': [{'wikipedia_id': '30030', 'title': 'Treaty of Versailles', 'start_paragraph_id': 1, 'start_character': 199, 'end_paragraph_id': 1, 'end_character': 211, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]