question: Who was Black Sabbath's lead vocalist from 1987 to 1991 and again from 1993 to 1997?
answerText: Tony Martin
questionEntity.name: Q47670
questionEntity.entityType: entity
questionEntity.label: Black Sabbath
questionEntity.mention: Black Sabbath's
questionEntity.name: 1987
questionEntity.entityType: date
questionEntity.mention: 1987
questionEntity.name: 1991
questionEntity.entityType: date
questionEntity.mention: 1991
questionEntity.name: 1993
questionEntity.entityType: date
questionEntity.mention: 1993
questionEntity.name: 1997
questionEntity.entityType: date
questionEntity.mention: 1997
answerEntity.name: Q434220
answerEntity.label: Tony Martin