Question: when did iron maiden release their first album
[{'answer': '14 April 1980', 'provenance': [{'wikipedia_id': '606884', 'title': 'Iron Maiden (album)', 'start_paragraph_id': 1, 'start_character': 107, 'end_paragraph_id': 1, 'end_character': 120, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]