Related Clues:

• Established
• Tried and true
• Established as fact
• Demonstrated
• Showed to be true
• No longer in doubt
• Tried-and-true
• Marked with a 'QED'
• Verified
• Shown as true
• Shown to be true
• Validated
• Like an ironclad case
• Adjective meaning demonstrated beyond doubt
• Provided evidence