Question: which supreme court case established the separate but equal doctrine
[{'answer': 'Plessy v. Ferguson', 'provenance': [{'wikipedia_id': '210031', 'title': 'Separate but equal', 'start_paragraph_id': 2, 'start_character': 35, 'end_paragraph_id': 2, 'end_character': 53, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '210031', 'title': 'Separate but equal', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 412, 'bleu_score': 0.894705322155054, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 5149520750655406868}, 'section': 'Section::::Abstract.'}]}]