Question: when was a right to unionize recognized by the federal government
[{'answer': '1914', 'provenance': [{'wikipedia_id': '1075686', 'title': 'United States labor law', 'start_paragraph_id': 2, 'start_character': 225, 'end_paragraph_id': 2, 'end_character': 229, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '1075686', 'title': 'United States labor law', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 953, 'bleu_score': 0.9411315128542521, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 458940630669032906}, 'section': 'Section::::Abstract.'}]}]