Possible Clues:

• Yippie Hoffman
• Activist Hoffman
• 'Steal This Book' author Hoffman
• 'Steal This Book' writer Hoffman
• Yippie name
• Yippies cofounder Hoffman
• Hoffman of the Chicago Seven
• "Steal This Book" author Hoffman
• Hoffman of the Yippies
• Youth International Party co-founder Hoffman