Question: who first used rr lyrae variable stars to determine distances in our milky way galaxy
[{'answer': 'E.C. Pickering'}, {'provenance': [{'wikipedia_id': '309428', 'title': 'RR Lyrae variable', 'start_paragraph_id': 5, 'start_character': 0, 'end_paragraph_id': 5, 'end_character': 141, 'bleu_score': 0.8151678595510181, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 9741098961248383213}, 'section': 'Section::::Discovery and recognition.\n'}]}]