<?xml version="1.0"?>
<!DOCTYPE root [
<!ELEMENT root ANY>
<!ATTLIST root attr1 CDATA #IMPLIED>
<!ATTLIST root attr2 CDATA #IMPLIED>
<!ENTITY aExternal SYSTEM "ibm41n11.ent">
<!ENTITY aIndirect "&aExternal;">
]>
<root attr1="&aIndirect;">indirect reference to external entinity in Attribute</root>