Related Clues:

• Established
• Tried and true
• Established as fact
• Demonstrated
• Certified
• Gave evidence for
• No longer in doubt
• Affirmed as true
• Marked with a 'QED'
• Vouched for
• Verified
• Shown as true
• Shown to be true
• Like an ironclad case
• Adjective meaning demonstrated beyond doubt