Small inline elements that surround a word or phrase in text because the subject (content) should be identified, such as the <named-content> element to identify a drug name, genus/species, product, etc.
At the time of these DTDs’ creation, there was only one phrase-level element. If more specific subject words (such as “gene”) are added to later versions of either DTD, they should be added to this entity.
<!ENTITY % phrase.class "abbrev" >
bookcustom-classes.ent