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) --> 13