Question: when was circus circus built in las vegas
[{'answer': '1968', 'provenance': [{'wikipedia_id': '721273', 'title': 'Circus Circus Las Vegas', 'start_paragraph_id': 3, 'start_character': 78, 'end_paragraph_id': 3, 'end_character': 82, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '721273', 'title': 'Circus Circus Las Vegas', 'start_paragraph_id': 5, 'start_character': 0, 'end_paragraph_id': 5, 'end_character': 289, 'bleu_score': 0.9560167778278961, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 9009458665325571479}, 'section': 'Section::::History.\n'}]}]