Type of Cross Reference


Indicates the type of element to which a cross reference is pointing (e.g., to a figure, an author note, a bibliographic reference citation, etc.). These values may be used for type-specific processing or validation.


The <xref> element may be used to reference anything that has an Identifier id attribute. This single element takes the place of the many named types of references (such as figure references, table references, and footnote references) that are common in many journal DTDs. This attribute preserves the information from such DTDs concerning the type of element to which the cross-reference is pointing.

Attribute Values

In Element

<xref> X(cross) Reference
Value Meaning
aff Affiliation
app Appendix
aunote Author note
bibr Bibliographic reference (to a <citation> or <ref> element)
boxed-text Textbox or sidebar
chem Chemical structure wrapper or chemical structure
contrib Contributor
corresp Corresponding author
disp-formula Display formula
fig Figure or figure group
fn Footnote
kwd Keyword
list List
plate Plate
scheme Scheme
sec Section
statement Statement
supplementary-material Supplementary material
table Table
table-fn A Footnote (<fn>) element that is found within a <table-wrap> element. Such footnotes should be displayed with the table rather than, for example, at the bottom of the page or screen.
other Something other than the named reference types
Restriction: This attribute may be specified if the element is used.