Related Clues:

• Some research aids
• Reference volumes
• Book with a big spine
• Ponderous volume
• Weighty book for my attention?
• A large book
• Volume’s dedication to its author?
• 'Leave it ___!' ('I got this!')
• Sao ___ and Principe
• It's bound to be big
• Volume of customers
• Big thick book
• A lot to read
• Hefty volume, in my opinion
• Where my letters are delivered in volume