Related Clues:

• Genius
• Brainiac
• Source of the quote
• See 42-Down
• See 58-Across
• A genius, relatively speaking
• See 18-Across
• Mastermind
• See 47-Down
• He was a genius, relatively speaking
• Brain
• Genius personified
• Relativity name
• Developer of the theory of relativity
• Brilliant person, as it were