Related Clues:

• Letters of introduction
• Reader's turns
• Book divisions
• Sea urchin's protection
• 17- and 65-Across, and 10- and 25-Down
• Book makeup
• Calls to the phone
• Senate workers
• Newspaper parts
• Knights-in-training
• Senate staffers
• Congress workers
• Library patrons read them
• Parts of books
• Knights' attendants