Related Clues:

• Letters to a mathematician
• Letters of proof
• Proof abbr
• Proof follow-up
• Where E is "erat"
• Letters seen by a proof reader?
• Math-proof letters
• Thus, in proofs
• End of many an argument
• Proof ending (Abbr.)
• Math text abbr.
• Letters at the end of a proof
• Argument-ending letters
• End-of-proof abbr.
• Logician's letters