Type of Cross-Reference

Type of element that is the target of the cross-reference (for example, “figure”, “author-note”, “bibliographic-reference”). The values may be used for type-specific processing or validation.


The <xref> element may be used to reference anything that has an @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 tag sets. This attribute preserves the information from such tag sets concerning the type of element to which the cross-reference is pointing.

With the Element

Value Meaning
aff Affiliation.
app Appendix.
author-notes Author notes.
bibr Bibliographic reference (typically to a <ref> element, but it may point to a <element-citation> or <mixed-citation> if there are multiple citations inside the <ref> element).
boxed-text Textbox or sidebar.
chem Chemical structure (to a <chem-struct> or <chem-struct-wrap> element).
contrib Contributor.
collab Collaboration.
corresp Corresponding author.
disp-formula Display formula.
fig Figure or group of figures (to a <fig> or <fig-group> element).
fn Footnote.
kwd Keyword.
list List or list item (to a <list> or <list-item> element; also, possibly to a <def-list> or <def-item> element).
other None of the items listed.
plate Plate.
scheme Scheme.
sec Section.
statement Statement.
supplementary-material Supplementary information.
table Table or group of tables (to a <table-wrap> or <table-wrap-group> element).
table-fn Table footnote.
Restriction: @ref-type is an optional attribute; there is no default.


<p>... The third nucleotide (CG<bold>A</bold>) at codon 529, which
is a specific nucleotide of <italic>M. tuberculosis</italic>
(<xref ref-type="bibr" rid="B8">8</xref>, <xref ref-type="bibr"
rid="B11">11</xref>), was not clearly determined ...</p>