Elements that can be included along with data characters inside the content model of the <volume-id> element
This Parameter Entity is currently set as %just-rendition;, which in turn is a null string, i.e., there is no string content. However, a customization module could redefine this Parameter Entity, thereby adding elements to the <volume-id> element.
<!ENTITY % volume-id-elements "%just-rendition; " >
common.ent