Elements that can be included along with data characters inside the content model of the structural title element (<title>)
Design Note: All inline mixes begin with an OR bar; since %simple-phrase; is an inline mix, the OR bar is already there and need not be added to %struct-title-elements;.
<!ENTITY % struct-title-elements "%simple-phrase; | %break.class; | %citation.class;" >
bookcustom-models.ent