1  <!DOCTYPE doc [
 2  <!ATTLIST doc attrExtEnt ENTITY #IMPLIED>
 3  <!ENTITY ent1 "Hello">
 4  <!ENTITY ent2 SYSTEM "world.txt">
 5  <!ENTITY entExt SYSTEM "earth.gif" NDATA gif>
 6  <!NOTATION gif SYSTEM "viewgif.exe">
 7  ]>
 8  <doc attrExtEnt="entExt">
 9     &ent1;, &ent2;!
10  </doc>
11  
12  <!-- Let world.txt contain "world" (excluding the quotes) -->