Possible Clues:

• Silverstein who wrote and illustrated 'The Giving Tree'
• Poet/cartoonist Silverstein
• Songwriter Silverstein
• Kids' author Silverstein
• Cartoonist Silverstein
• Silverstein who wrote "The Giving Tree"
• Children's poet Silverstein
• 'A Boy Named Sue' writer Silverstein
• "Falling Up" author Silverstein
• Silverstein who wrote the words and music for Johnny Cash's 'A Boy Named Sue'