<xs:complexType name="periodicalMailHeaderType"> <xs:sequence> <xs:element name="PublicationNumber" type="mailxml_base:ns09" /> <xs:element name="IssueDate" type="xs:dateTime" /> <xs:element name="IssueNumber" type="mailxml_base:ns06" minOccurs="0" /> <xs:element name="VolumeNumber" type="mailxml_base:ns05" minOccurs="0" /> </xs:sequence> </xs:complexType>