Question: when did the first justice league come out
[{'answer': 'March 1960', 'provenance': [{'wikipedia_id': '99940', 'title': 'Justice League', 'start_paragraph_id': 1, 'start_character': 505, 'end_paragraph_id': 1, 'end_character': 515, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]