Question: when did labor unions begin to gain some legal rights in the united states
[{'answer': 'in the 1930s', 'provenance': [{'wikipedia_id': '2474406', 'title': 'Labor unions in the United States', 'start_paragraph_id': 9, 'start_character': 96, 'end_paragraph_id': 9, 'end_character': 108, 'bleu_score': 1.0, 'section': 'Section::::History.\n'}]}, {'provenance': [{'wikipedia_id': '2474406', 'title': 'Labor unions in the United States', 'start_paragraph_id': 9, 'start_character': 0, 'end_paragraph_id': 9, 'end_character': 338, 'bleu_score': 0.962600167205617, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 14766547804483212143}, 'section': 'Section::::History.\n'}]}]