Who was Black Sabbath's lead vocalist from 1987 to 1991 and again from 1993 to 1997?
{'directed': True, 'multigraph': False, 'graph': {}, 'nodes': [{'type': 'INTERNAL', 'name_': 'Q1860', 'id': 0, 'label': 'English'}, {'type': 'INTERNAL', 'name_': 'Q150', 'id': 1, 'label': 'French'}, {'type': 'INTERNAL', 'name_': 'Q24314', 'id': 2, 'label': 'Born Again'}, {'type': 'QUESTIONS_ENTITY', 'name_': 'Q47670', 'id': 3, 'label': 'Black Sabbath'}, {'type': 'INTERNAL', 'name_': 'Q1212326', 'id': 4, 'label': 'The Family of the Vourdalak'}, {'type': 'ANSWER_CANDIDATE_ENTITY', 'name_': 'Q2270855', 'id': 5, 'label': 'Black Sabbath'}], 'links': [{'name_': 'P737', 'source': 0, 'target': 1, 'label': 'influenced by'}, {'name_': 'P407', 'source': 2, 'target': 0, 'label': 'language of work or name'}, {'name_': 'P175', 'source': 2, 'target': 3, 'label': 'performer'}, {'name_': 'P407', 'source': 4, 'target': 1, 'label': 'language of work or name'}, {'name_': 'P4969', 'source': 4, 'target': 5, 'label': 'derivative work'}]}