<xsd:group name="prefaceContainers">
  <xsd:annotation>
    <xsd:documentation>
      <type>Group</type>
      <name>prefaceContainers</name>
      <comment>The group prefaceContainers lists the elements that are containers and are specific to the Akoma Ntoso preface vocabulary</comment>
    </xsd:documentation>
  </xsd:annotation>
  <xsd:choice>
    <xsd:element ref="longTitle"/>
    <xsd:element ref="formula"/>
    <xsd:element ref="container"/>
  </xsd:choice>
</xsd:group>