Question: when did mlk lead protesters through memphis in support of sanitation workers
[{'answer': 'February 1968', 'provenance': [{'wikipedia_id': '13206035', 'title': 'Memphis sanitation strike', 'start_paragraph_id': 1, 'start_character': 39, 'end_paragraph_id': 1, 'end_character': 52, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '13206035', 'title': 'Memphis sanitation strike', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 622, 'bleu_score': 0.9806740509884301, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 4061892905563153035}, 'section': 'Section::::Abstract.'}]}]