glossrefGlossary reference topic references are a convenience element for creating references to glossary topics. It has a required @keys attribute, which forces the author to create a key by which inline terms can reflect the glossary terms and become navigable links to the glossary definition. For example, when <glossentry> topics are used to define acronyms, this reminds authors to create a key that <abbreviated-form> elements can use to refer to the short and expanded versions of the acronyms.