<?xml version='1.0' encoding='utf-8'?>

<xs:schema
  	elementFormDefault="qualified"
  	attributeFormDefault="unqualified"
  	xmlns:xs="http://www.w3.org/2001/XMLSchema"
  	>

  <xs:simpleType name="relation_supplement_Enum">
    <xs:union>
      <xs:simpleType>
        <xs:restriction base="xs:normalizedString">
          <xs:whiteSpace value='collapse'/>
           <xs:enumeration value='Atlas'/>
           <xs:enumeration value='Bibliography(s)'/>
           <xs:enumeration value='Biographical information'/>
           <xs:enumeration value='Contextual information'/>
           <xs:enumeration value='Essay(s)'/>
           <xs:enumeration value='Related web sites'/>
           <xs:enumeration value='Teacher and student resources'/>
      	</xs:restriction>
      </xs:simpleType>
    </xs:union>
  </xs:simpleType>
</xs:schema>