A list of bibliographic descriptions of material, for example, descriptions of journal articles or other books cited by this work. The list typically has a title such as “References”, “Bibliography”, or “Additional Reading”. This Tag Set makes no distinction between lists of cited references and lists of suggested references; both would be tagged as <ref-list>. This Tag Library will refer to these lists as references lists or as bibliographic references lists.

One item in a bibliographic references list. Each item may be numbered, take a prefix symbol, or a prefixed designator such as [Lapeyre 2009]. A <ref> is not a textual description of cited material, but it may contain one or more such descriptions or it may contain a note. A very typical <ref> contains the description of one work inside a citation element (<element-citation> or <mixed-citation>).

A <ref> does not contain text directly because some publishers place multiple works into a single numbered item in a bibliographic reference list. The <ref> is the element for that item. Each cited work will be contained in a citation element (<element-citation> or <mixed-citation>).

The bibliographic description of a single work, such as a journal article, conference proceeding, or book. This element will contain text, bibliographic elements, or a mixture of the two, for example, listing the title of a work, the author, the date of publication, the page in the journal on which the article starts, and similar information.

Single citations are almost never numbered or given a prefix designator because the prefix and identifying attribute are placed on the containing <ref> element. But citations are allowed to take numbers or designators (<label>) to handle those cases where a single item in a reference list describes multiple works.

Inside the text of a work, it is common to refer to (cite) external sources such as journal articles that were influential in forming the ideas expressed in that part of the text. These too are commonly called “citations”. This Tag Set will use the term cross-reference (the element <xref>) to name the text that points to the description of a cited work in a bibliographic references list. The @ref-type on the <xref> can be set to “bibr” to indicate that the cross-reference is pointing to an item in a reference list. Typically, the @rid attribute will point the unique identifier (@id) of a <ref>. But when a <ref> contains multiple citations, the @rid may point to the identifier of a particular citation (<element-citation> or <mixed-citation>).