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.
<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>