<?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>