Related Clues:

• Baseball card factoid
• "Immediately!" in 20-Across
• Something known to be true
• It's certainly not fiction
• "Immediately!"
• Statement of verifiable information
• Actually, it's in here
• This might be the whole truth - or afterwards only contributory to it
• Actually, you'll find it in this
• It's the turn of Ulster to start in formation, perhaps
• Actually it's in this, or it's added to make it mathematical
• It's true that it sounds as if Arty might build on it
• In this it would be actually non-fiction
• Doctor's imperative
• BA or HR