Question: what type of literature from what period of history constitutes our earliest source of greek myths
[{'answer': 'Ancient Greek literature', 'provenance': [{'wikipedia_id': '18963870', 'title': 'Literature', 'start_paragraph_id': 19, 'start_character': 186, 'end_paragraph_id': 19, 'end_character': 210, 'bleu_score': 1.0, 'section': 'Section::::History.\n'}]}, {'provenance': [{'wikipedia_id': '18963870', 'title': 'Literature', 'start_paragraph_id': 19, 'start_character': 0, 'end_paragraph_id': 19, 'end_character': 903, 'bleu_score': 0.9858648355536391, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 17715548274283507301}, 'section': 'Section::::History.\n'}]}]