<?xml version="1.0" encoding="UTF-8" ?>
<customers>
<customer ref="1">
<order>
<!-- Order details-->
<invoice number="1-1" date="YYYYYY"/>
</order>
<order>
<!-- Order details-->
<invoice number="1-2" date="YYYYYY"/>
</order>
</customer>
<customer ref="2">
<order>
<!-- Order details-->
<invoice number="2-1" date="YYYYYY"/>
</order>
<order>
<!-- Order details-->
<invoice number="2-2" date="YYYYYY"/>
</order>
<order>
<!-- Order details-->
<invoice number="2-3" date="YYYYYY"/>
</order>
</customer>
</customers>