custom-info 

Any other information about the book/document that didnt fit in the above groups

Element Information

Model

Attributes

QName Type Fixed Default Use Inheritable Annotation
info-type xs:string required
xml:lang xs:language optional 
Element content's languige

Source 

<xs:element name="custom-info" minOccurs="0" maxOccurs="unbounded">
  <xs:annotation>
    <xs:documentation>Any other information about the book/document that didnt fit in the above groups</xs:documentation>
  </xs:annotation>
  <xs:complexType>
    <xs:simpleContent>
      <xs:extension base="textFieldType">
        <xs:attribute name="info-type" type="xs:string" use="required"/>
      </xs:extension>
    </xs:simpleContent>
  </xs:complexType>
</xs:element>

Sample