Question: when was the us national park system established
[{'answer': 'June 10 , 1933'}, {'provenance': [{'wikipedia_id': '19187901', 'title': 'History of the National Park Service', 'start_paragraph_id': 21, 'start_character': 0, 'end_paragraph_id': 21, 'end_character': 352, 'bleu_score': 0.797029305124023, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 9200046235090675037}, 'section': 'Section::::Reorganization of 1933.\n'}]}]