<?xml version="1.0" standalone="yes"?>
<!DOCTYPE Catalog[
<!ENTITY loc "Library of Congress">
<!ELEMENT Catalog (Book+)>
<!ELEMENT Book (Title,Author*,Publisher*,Pub_Date*)>
<!ELEMENT Title (#PCDATA)*>
<!ATTLIST Title ISBN CDATA #REQUIRED>
<!ELEMENT Author (#PCDATA)*>
<!ATTLIST Author Status CDATA #IMPLIED>
<!ELEMENT Publisher (#PCDATA)*>
<!ELEMENT Pub_Date (#PCDATA)*>
]>
<!-- Begin Document Body -->
<Catalog>
. . .
</Catalog>