Question: when did superman first appear in a comic book
[{'answer': 'April 18 , 1938', 'provenance': [{'wikipedia_id': '28381', 'title': 'Superman', 'start_paragraph_id': 15, 'start_character': 109, 'end_paragraph_id': 15, 'end_character': 124, 'bleu_score': 1.0, 'section': 'Section::::Creation and conception.\n'}]}]