Synonyms:
  1. absolute indication
  2. clue
  3. conclusive evidence
  4. corroboration
  5. damning evidence
  6. documentation
  7. evidence
  8. incontrovertible evidence
  9. indisputable evidence
  10. proof
  11. straw-in-the-wind
  12. substantiation
  13. support
  14. sure sign
  15. telltale
  16. tip-off
  17. unmistakable sign
  18. verification