Question: when did the ground rule double go into effect
[{'answer': '1930', 'provenance': [{'wikipedia_id': '1039434', 'title': 'Ground rule double', 'start_paragraph_id': 8, 'start_character': 201, 'end_paragraph_id': 8, 'end_character': 205, 'bleu_score': 1.0, 'section': 'Section::::History.\n'}]}, {'provenance': [{'wikipedia_id': '1039434', 'title': 'Ground rule double', 'start_paragraph_id': 8, 'start_character': 0, 'end_paragraph_id': 8, 'end_character': 469, 'bleu_score': 0.652139491112623, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 15639318828261951370}, 'section': 'Section::::History.\n'}]}]