<?xml version="1.0" encoding="UTF-8" standalone="yes" ?>
<!DOCTYPE gml SYSTEM "http://www.gamgi.org/dtd/gamgi.dtd"
[
<!ENTITY outside1 SYSTEM "document1.xml"> 
<!ENTITY outside2 SYSTEM "document2.xml"> 
<!ENTITY inside0 "<atom element='O' x='0.0' y='0.0' z='0.0'/>"> 
<!ENTITY inside1 "<layer>&inside0;</layer>"> 
]>
<gml>
  <gamgi>
  <atom style="solid"/>
  <bond style="solid"/>
  </gamgi>
  <bond parent1="C1" parent2="C3"></bond>
  <bond parent1="C2" parent2="C4"></bond>
  <window> &inside1; </window>
  &outside1;
  <gamgi>
  <atom style=""/>
  <bond style=""/>
  </gamgi>
</gml>
