## Description

XREF defines one reference to the bibliographic data. The contents of the element describes the ID or the citation key of a single entry in the bibliographic database. This string always starts with "ID".

The ENDTERM attribute starts with the string "IM". The remainder is a number which is incremented with each multiple citation, starting at 0.

## Example

    <CITATIONLIST>
    <CITATION>
    <XREF>IDNAKANE2002</XREF>
    </CITATION>
    <CITATION>
    <XREF ENDTERM="IM0">IDNAKANE2002</XREF>
    <XREF>IDNAKANE2002</XREF>
    <XREF>IDCERWINKA2002</XREF>
    <XREF>IDMIZUSAWA2002</XREF>
    </CITATION>
    <XREF>1</XREF>
    </CITATION>
    </CITATIONLIST>