External module in the Book Tag Set (and Collection Tag Set) that sets up the parameter entities and element mix definitions that will be used to override some element mixes in the Suite
<!ENTITY % bookcustom-mixes.ent PUBLIC "-//NLM//DTD NCBI Book DTD Over-ride Mixes Module v3.0 20080202//EN" "bookcustom-mixes3.ent" >
bookcustom-modules3.ent