A sign designates a shelf holding study materials for Airmen and their family members inside the Holbrook Library at Ellsworth Air Force Base, S.D., July 26th, 2018. One thing added to the Holbrook Library is an entirely new organizational system that is based on what category the books fall into, such as CLEP and DANTES study books. (U.S. Air Force photo by Amn John Ennis)