<!ELEMENT Invoice (Header,Item+)>
<!ELEMENT Header (Date,BillTo)>
<!ATTLIST Header
 invoiceNumber CDATA #REQUIRED
>
<!ELEMENT Item (description*)>
<!ATTLIST Item
 price CDATA #REQUIRED
 discount (promotion | regular) "regular"
>
<!ELEMENT Date ((Month,Day,Year)|(Day,Month,Year))>
<!ELEMENT BillTo (Address)>
<!ATTLIST BillTo
 custNumber ID #REQUIRED
 name CDATA #IMPLIED
 phone CDATA #IMPLIED
>
<!ELEMENT description (#PCDATA)>
<!ELEMENT Address (street1,street2?,city,(state|province),zip,country?)>
<!ELEMENT street1 (#PCDATA)>
<!ELEMENT street2 (#PCDATA)>
<!ELEMENT city (#PCDATA)>
<!ELEMENT state (#PCDATA)>
<!ELEMENT province (#PCDATA)>
<!ELEMENT zip (#PCDATA)>
<!ELEMENT country (#PCDATA)>
<!ELEMENT Month (#PCDATA)>
<!ELEMENT Day (#PCDATA)>
<!ELEMENT Year (#PCDATA)>