Related Clues:

• Final comment I add to letter in Greek
• Letter: its last words might be '- love you'
• Secretary's first to open one letter, then another
• Pounds per sq. in. (abbr.)
• Modern Greek character's past it, oddly enough
• One added to letter, and one more letter
• Greek letter; pressure unit
• Greek letter; pounds per square inch (abbrev.)
• Inflation indication: Abbr
• Symbol for Freud's field
• Follower of chi
• Fraternity letter shaped like a trident
• In addition I got a letter from abroad
• Sigma initially included by one Greek character or another
• 'A letter', you say unhappily, reading it aloud