<rules
    xmlns="http://namespaces.plone.org/xdv"
    xmlns:css="http://namespaces.plone.org/xdv+css"
    >

    <replace css:theme="#include" css:content="#something" href="extra.html" method="esi"/>
    <replace css:theme="#include-fragment" href="fragment.html" method="esi"/>

</rules>
