carbon_ref.xml

<?xml version="1.0" encoding="UTF-8"?>
<fpmd:species name="carbon" xlink:href="carbon.xml"
  xmlns:fpmd="http://www.quantum-simulation.org/ns/fpmd/fpmd-1.0" 
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
  xmlns:xlink="http://www.w3.org/1999/xlink"
  xsi:schemaLocation="http://www.quantum-simulation.org/ns/fpmd/fpmd-1.0 
  species.xsd">
</fpmd:species>