Credo's Add-on Content consists of specialized titles that are available as add-ons to your existing Core Collection, or as a stand-alone content for institutions that do not already subscribe to Credo. Add-on Content is available for perpetual purchase. You can see a list of all titles available here.
Additionally, Credo's Essentials Collections are available for subscription. These collections bring together top-tier, award-winning, classic, and peer-acclaimed reference titles, and are regularly updated with the latest content. You can see a list of Essentials Collections here.